Event support for Mail merge

4 Apr 202324 minutes to read

The MailMerge class provides event support to customize the document contents and merging image data during the Mail merge process. The following events are supported by Essential DocIO during Mail merge process:

MergeField Event

You can apply formatting to the merged text or customize the merged text during mail merge process using the MergeField Event.

The following code example shows how to use the MergeField event during Mail merge process.

//Opens the template document 
FileStream fileStreamPath = new FileStream("Template.docx", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
WordDocument document = new WordDocument(fileStreamPath, FormatType.Docx);  
//Uses the mail merge events to perform the conditional formatting during runtime
document.MailMerge.MergeField += new MergeFieldEventHandler(ApplyAlternateRecordsTextColor);
//Executes Mail Merge with groups
document.MailMerge.ExecuteGroup(GetDataTable());
//Saves the Word document to MemoryStream
MemoryStream stream = new MemoryStream();
document.Save(stream, FormatType.Docx);
//Closes the Word document
document.Close();
//Opens the template document 
WordDocument document = new WordDocument("Template.docx");    
//Uses the mail merge events to perform the conditional formatting during runtime
document.MailMerge.MergeField += new MergeFieldEventHandler(ApplyAlternateRecordsTextColor);
//Executes Mail Merge with groups
document.MailMerge.ExecuteGroup(GetDataTable());
//Saves and closes the Word document instance
document.Save("Sample.docx");
document.Close();
'Opens the template document 
Dim document As New WordDocument("Template.docx")
'Uses the mail merge events to perform the conditional formatting during runtime
AddHandler document.MailMerge.MergeField, AddressOf ApplyAlternateRecordsTextColor
'Executes Mail Merge with groups
document.MailMerge.ExecuteGroup(GetDataTable())
'Saves and closes the Word document instance
document.Save("Sample.docx")
document.Close()
//ADO.NET object is supported in Windows Forms, WPF, ASP.NET, ASP.NET MVC, ASP.NET Core, and Xamarin platforms alone.

The following code example shows how to set text color to the alternate Mail merge record by using MergeFieldEventHandler.

private void ApplyAlternateRecordsTextColor (object sender, MergeFieldEventArgs args)
{
    //Sets text color to the alternate mail merge record
    if (args.RowIndex % 2 == 0)
    {
        args.TextRange.CharacterFormat.TextColor = Color.FromArgb(255, 102, 0);
    }
}
private void ApplyAlternateRecordsTextColor (object sender, MergeFieldEventArgs args)
{
    //Sets text color to the alternate mail merge record
    if (args.RowIndex % 2 == 0)
    {
        args.TextRange.CharacterFormat.TextColor = Color.FromArgb(255, 102, 0);
    }
}
Private Sub ApplyAlternateRecordsTextColor(ByVal sender As Object, ByVal args As MergeFieldEventArgs)
    'Sets text color to the alternate mail merge record
    If ((args.RowIndex Mod 2) = 0) Then
        args.TextRange.CharacterFormat.TextColor = Color.FromArgb(255, 102, 0)
    End If
End Sub
//ADO.NET object is supported in Windows Forms, WPF, ASP.NET, ASP.NET MVC, ASP.NET Core, and Xamarin platforms alone.

NOTE

While executing mail merge, DocIO internally uses a copy of a particular region for populating the contents. Sometimes, unexpected problems may arise due to inserting multiple body items into the region through the mail merge process. So, to insert multiple body items using the merge field event handler, you are recommended to use this approach at your side.

The following code example shows GetDataTable method which is used to get data for mail merge.

private static DataTable GetDataTable()
{
    DataTable dataTable = new DataTable("Employee");
    dataTable.Columns.Add("EmployeeName");
    dataTable.Columns.Add("EmployeeNumber");
    for (int i = 0; i < 20; i++)
    {
        DataRow datarow = dataTable.NewRow();
        dataTable.Rows.Add(datarow);
        datarow[0] = "Employee" + i.ToString();
        datarow[1] = "EMP" + i.ToString();
    }
    return dataTable;
}
private static DataTable GetDataTable()
{
    DataTable dataTable = new DataTable("Employee");
    dataTable.Columns.Add("EmployeeName");
    dataTable.Columns.Add("EmployeeNumber");
    for (int i = 0; i < 20; i++)
    {
        DataRow datarow = dataTable.NewRow();
        dataTable.Rows.Add(datarow);
        datarow[0] = "Employee" + i.ToString();
        datarow[1] = "EMP" + i.ToString();
    }
    return dataTable;
}
Private Function GetDataTable() As DataTable
    Dim dataTable As New DataTable("Employee")
    dataTable.Columns.Add("EmployeeName")
    dataTable.Columns.Add("EmployeeNumber")
    For i As Integer = 0 To 19
        Dim datarow As DataRow = dataTable.NewRow()
        dataTable.Rows.Add(datarow)
        datarow(0) = "Employee" + i.ToString()
        datarow(1) = "EMP" + i.ToString()
    Next
    Return dataTable
End Function
//ADO.NET object is supported in Windows Forms, WPF, ASP.NET, ASP.NET MVC, ASP.NET Core, and Xamarin platforms alone.

You can download a complete working sample from GitHub.

MergeImageField Event

You can format the merged image like resizing the image and more during mail merge process using the MergeImageField Event.

The following code example shows how to use the MergeImageField event during Mail merge process.

//Opens the template document
FileStream fileStreamPath = new FileStream("Template.docx", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
WordDocument document = new WordDocument(fileStreamPath, FormatType.Docx);
//Uses the mail merge events handler for image fields
document.MailMerge.MergeImageField += new MergeImageFieldEventHandler(MergeField_ProductImage);
//Specifies the field names and field values
string[] fieldNames = new string[] { "Logo"};
string[] fieldValues = new string[] { "Logo.png"};
//Executes the mail merge with groups
document.MailMerge.Execute(fieldNames, fieldValues);
//Saves the Word document to MemoryStream
MemoryStream stream = new MemoryStream();
document.Save(stream, FormatType.Docx);
//Closes the Word document
document.Close();
//Opens the template document
WordDocument document = new WordDocument("Template.docx");
//Uses the mail merge events handler for image fields
document.MailMerge.MergeImageField += new MergeImageFieldEventHandler(MergeField_ProductImage);
//Specifies the field names and field values
string[] fieldNames = new string[] { "Logo"};
string[] fieldValues = new string[] { "Logo.png"};
//Executes the mail merge with groups
document.MailMerge.Execute(fieldNames, fieldValues);
//Saves and closes WordDocument instance
document.Save("Sample.docx");
document.Close();
'Opens the template document
Dim document As New WordDocument("Template.docx")
'Uses the mail merge events handler for image fields
AddHandler document.MailMerge.MergeImageField, AddressOf MergeField_ProductImage
'Specifies the field names and field values
Dim fieldNames As String() = New String() {"Logo"}
Dim fieldValues As String() = New String() {"Logo.png"}
'Executes the mail merge with groups
document.MailMerge.Execute(fieldNames, fieldValues)
'Saves and closes WordDocument instance
document.Save("Sample.docx")
document.Close()

The following code example shows how to bind the image from file system during Mail merge process by using MergeImageFieldEventHandler.

private void MergeField_ProductImage(object sender, MergeImageFieldEventArgs args)
{
    //Binds image from file system during mail merge
    if (args.FieldName == "Logo")
    {
        string ProductFileName = args.FieldValue.ToString();
        //Gets the image from file system
        FileStream imageStream = new FileStream(ProductFileName, FileMode.Open, FileAccess.Read);
        args.ImageStream = imageStream;
        //Gets the picture, to be merged for image merge field
        WPicture picture = args.Picture;
        //Resizes the picture
        picture.Height = 50;
        picture.Width = 150;
    }
}
private void MergeField_ProductImage(object sender, MergeImageFieldEventArgs args)
{
    //Binds image from file system during mail merge
    if (args.FieldName == "Logo")
    {
        string ProductFileName = args.FieldValue.ToString();
        //Gets the image from file system
        args.Image = Image.FromFile(ProductFileName);
        //Gets the picture, to be merged for image merge field
        WPicture picture = args.Picture;
        //Resizes the picture
        picture.Height = 50;
        picture.Width = 150;
    }
}
Private Sub MergeField_ProductImage(ByVal sender As Object, ByVal args As MergeImageFieldEventArgs)
    'Binds image from file system during mail merge
    If args.FieldName = "Logo" Then
        Dim ProductFileName As String = args.FieldValue.ToString()
        'Gets the image from file system
        args.Image = Image.FromFile(ProductFileName)
        'Gets the picture, to be merged for image merge field
        Dim picture As WPicture = args.Picture
        'Resizes the picture
        picture.Height = 50
        picture.Width = 150
    End If
End Sub

You can download a complete working sample from GitHub.

BeforeClearField Event

You can get the unmerged fields in a Word document during mail merge process using the BeforeClearField Event.

The following code example shows how to use the BeforeClearField event during Mail merge process.

//Opens the template document 
FileStream fileStreamPath = new FileStream("Template.docx", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
WordDocument document = new WordDocument(fileStreamPath);
//Sets “ClearFields” to true to remove empty mail merge fields from document
document.MailMerge.ClearFields = false;
//Uses the mail merge event to clear the unmerged field while perform mail merge execution
document.MailMerge.BeforeClearField += new BeforeClearFieldEventHandler(BeforeClearFieldEvent);
//Execute mail merge
document.MailMerge.ExecuteGroup(GetDataTable());
//Saves the Word document to MemoryStream
MemoryStream stream = new MemoryStream();
document.Save(stream, FormatType.Docx);
//Closes the Word document
document.Close();
//Opens the template document 
WordDocument document = new WordDocument("Template.docx");
//Sets “ClearFields” to true to remove empty mail merge fields from document
document.MailMerge.ClearFields = false;
//Uses the mail merge event to clear the unmerged field while perform mail merge execution
document.MailMerge.BeforeClearField += new BeforeClearFieldEventHandler(BeforeClearFieldEvent);
//Execute mail merge
document.MailMerge.ExecuteGroup(GetDataTable());
//Saves and closes the WordDocument instance
document.Save("Sample.docx");
document.Close();
'Opens the template document 
Dim document As WordDocument = New WordDocument("Template.docx")
'Sets “ClearFields” to true to remove empty mail merge fields from document
document.MailMerge.ClearFields = False
'Uses the mail merge event to clear the unmerged field while perform mail merge execution
document.MailMerge.BeforeClearField += New BeforeClearFieldEventHandler(AddressOf BeforeClearField)
'Execute mail merge
document.MailMerge.ExecuteGroup(GetDataTable())
'Saves and closes the WordDocument instance
document.Save("Sample.docx")
document.Close()
//ADO.NET object is supported in Windows Forms, WPF, ASP.NET, ASP.NET MVC, ASP.NET Core, and Xamarin platforms alone.

The following code example shows how to bind the data to unmerged fields during Mail merge process by using BeforeClearFieldEventHandler.

private void BeforeClearFieldEvent (object sender, BeforeClearFieldEventArgs args)
{
    if (args.HasMappedFieldInDataSource)
    {
        //To check whether the mapped field has null value
        if (args.FieldValue == null || args.FieldValue == DBNull.Value)
        {
            //Gets the unmerged field name.
            string unmergedFieldName = args.FieldName;
            string ownerGroup = args.GroupName;
            //Sets error message for unmerged fields.
            args.FieldValue = "Error! The value of MergeField " + unmergedFieldName + " of owner group " + ownerGroup + " is defined as Null in the data source.";
        }
        else
            //If field value is empty, you can set whether the unmerged merge field can be clear or not.
            args.ClearField = true;
    }
    else
    {
        string unmergedFieldName = args.FieldName;
        //Sets error message for unmerged fields, which is not found in data source.
        args.FieldValue = "Error! The value of MergeField " + unmergedFieldName + " is not found in the data source.";
    }
}
private void BeforeClearFieldEvent (object sender, BeforeClearFieldEventArgs args)
{
    if (args.HasMappedFieldInDataSource)
    {
        //To check whether the mapped field has null value
        if (args.FieldValue == null || args.FieldValue == DBNull.Value)
        {
            //Gets the unmerged field name
            string unmergedFieldName = args.FieldName;
            string ownerGroup = args.GroupName;
            //Sets error message for unmerged fields
            args.FieldValue = "Error! The value of MergeField " + unmergedFieldName + " of owner group " + ownerGroup + " is defined as Null in the data source.";
        }
        else
            //If field value is empty, you can set whether the unmerged merge field can be clear or not
            args.ClearField = true;
    }
    else
    {
        string unmergedFieldName = args.FieldName;
        //Sets error message for unmerged fields, which is not found in data source
        args.FieldValue = "Error! The value of MergeField " + unmergedFieldName + " is not found in the data source.";
    }
}
Private Sub BeforeClearField(ByVal sender As Object, ByVal args As BeforeClearFieldEventArgs)
    If args.HasMappedFieldInDataSource Then
        'To check whether the mapped field has null value
        If args.FieldValue Is Nothing OrElse args.FieldValue = DBNull.Value Then
            'Gets the unmerged field name
            Dim unmergedFieldName As String = args.FieldName
            Dim ownerGroup As String = args.GroupName
            'Sets error message for unmerged fields
            args.FieldValue = "Error! The value of MergeField " & unmergedFieldName & " of owner group " & ownerGroup & " is defined as Null in the data source."
        Else
            'If field value is empty, you can set whether the unmerged merge field can be clear or not
            args.ClearField = True
    End If
    Else
        Dim unmergedFieldName As String = args.FieldName
        'Sets error message for unmerged fields, which is not found in data source
        args.FieldValue = "Error! The value of MergeField " & unmergedFieldName & " is not found in the data source."
    End If
End Sub
//ADO.NET object is supported in Windows Forms, WPF, ASP.NET, ASP.NET MVC, ASP.NET Core, and Xamarin platforms alone.

The following code example shows GetDataTable method which is used to get data for mail merge.

private DataTable GetDataTable()
{
    //Create an instance of DataTable
    DataTable dataTable = new DataTable("Employee");
    //Add columns
    dataTable.Columns.Add("EmployeeId");
    dataTable.Columns.Add("City");
    //Add records
    DataRow row;
    row = dataTable.NewRow();
    row["EmployeeId"] = "1001";
    row["City"] = null;
    dataTable.Rows.Add(row);
    row = dataTable.NewRow();
    row["EmployeeId"] = "1002";
    row["City"] = "";
    dataTable.Rows.Add(row);
    row = dataTable.NewRow();
    row["EmployeeId"] = "1003";
    row["City"] = "London";
    dataTable.Rows.Add(row);
    return dataTable;
}
private DataTable GetDataTable()
{
    //Create an instance of DataTable
    DataTable dataTable = new DataTable("Employee");
    //Add columns
    dataTable.Columns.Add("EmployeeId");
    dataTable.Columns.Add("City");
    //Add records
    DataRow row;
    row = dataTable.NewRow();
    row["EmployeeId"] = "1001";
    row["City"] = null;
    dataTable.Rows.Add(row);
    row = dataTable.NewRow();
    row["EmployeeId"] = "1002";
    row["City"] = "";
    dataTable.Rows.Add(row);
    row = dataTable.NewRow();
    row["EmployeeId"] = "1003";
    row["City"] = "London";
    dataTable.Rows.Add(row);
    return dataTable;
}
Private Function GetDataTable() As DataTable
    'Create an instance of DataTable
    Dim dataTable As DataTable = New DataTable("Employee")
    'Add columns
    dataTable.Columns.Add("EmployeeId")
    dataTable.Columns.Add("City")
    'Add records
    Dim row As DataRow
    row = dataTable.NewRow()
    row("EmployeeId") = "1001"
    row("City") = Nothing
    dataTable.Rows.Add(row)
    row = dataTable.NewRow()
    row("EmployeeId") = "1002"
    row("City") = ""
    dataTable.Rows.Add(row)
    row = dataTable.NewRow()
    row("EmployeeId") = "1003"
    row("City") = "London"
    dataTable.Rows.Add(row)
    Return dataTable
End Function
//ADO.NET object is supported in Windows Forms, WPF, ASP.NET, ASP.NET MVC, ASP.NET Core, and Xamarin platforms alone.

You can download a complete working sample from GitHub.

BeforeClearGroupField Event

You can get the unmerged group fields in a Word document during mail merge process using the BeforeClearGroupField event.

The following code example shows how to use the BeforeClearGroupField event during Mail merge process.

//Opens the template document
FileStream fileStreamPath = new FileStream("Template.docx", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
WordDocument document = new WordDocument(fileStreamPath, FormatType.Docx);
//Sets “ClearFields” to true to remove empty mail merge fields from document
document.MailMerge.ClearFields = false;
//Uses the mail merge event to clear the unmerged group field while perform mail merge execution
document.MailMerge.BeforeClearGroupField += new BeforeClearGroupFieldEventHandler(BeforeClearFields);
//Gets the employee details as “IEnumerable” collection
List<Employees> employeeList = GetEmployees();
//Creates an instance of “MailMergeDataTable” by specifying mail merge group name and “IEnumerable” collection
MailMergeDataTable dataTable = new MailMergeDataTable("Employees", employeeList);
//Performs Mail merge
document.MailMerge.ExecuteNestedGroup(dataTable);
//Saves the Word document to MemoryStream
MemoryStream stream = new MemoryStream();
document.Save(stream, FormatType.Docx);
//Closes the Word document
document.Close();
//Opens the template document 
WordDocument document = new WordDocument("Template.docx");
//Sets “ClearFields” to true to remove empty mail merge fields from document
document.MailMerge.ClearFields = false;
//Uses the mail merge event to clear the unmerged group field while perform mail merge execution
document.MailMerge.BeforeClearGroupField += new BeforeClearGroupFieldEventHandler(BeforeClearFields);
//Gets the employee details as “IEnumerable” collection
List<Employees> employeeList = GetEmployees();
//Creates an instance of “MailMergeDataTable” by specifying mail merge group name and “IEnumerable” collection
MailMergeDataTable dataTable = new MailMergeDataTable("Employees", employeeList);
//Performs Mail merge
document.MailMerge.ExecuteNestedGroup(dataTable);
//Saves and closes the WordDocument instance
document.Save("Sample.docx");
document.Close();
'Opens the template document 
Dim document As WordDocument = New WordDocument("Template.docx")
'Sets “ClearFields” to true to remove empty mail merge fields from document
document.MailMerge.ClearFields = False
'Uses the mail merge event to clear the unmerged field while perform mail merge execution
AddHandler document.MailMerge.BeforeClearGroupField, AddressOf BeforeClearFields
'Gets the employee details as “IEnumerable” collection
Dim employeeList As List(Of Employees) = GetEmployees()
'Creates an instance of MailMergeDataTableby specifying mail merge group name and “IEnumerable” collection
Dim dataTable As MailMergeDataTable = New MailMergeDataTable("Employees", employeeList)
'Performs Mail merge
document.MailMerge.ExecuteNestedGroup(dataTable)
'Saves and closes the WordDocument instance
document.Save("Sample.docx")
document.Close()

The following code example shows how to bind the data to unmerged group fields during Mail merge process by using BeforeClearGroupFieldEventHandler.

private static void BeforeClearFields(object sender, BeforeClearGroupFieldEventArgs args)
{
    if (!args.HasMappedGroupInDataSource)
    {
        //Gets the Current unmerged group name from the event argument
        string[] groupName = args.GroupName.Split(':');
        if (groupName[groupName.Length - 1] == "Orders")
        {
            string[] fields = args.FieldNames;
            List<OrderDetails> orderList = GetOrders();
            //Binds the data to the unmerged fields in group as alternative values
            args.AlternateValues = orderList;
        }
        else
            //If group value is empty, you can set whether the unmerged merge group field can be clear or not.
            args.ClearGroup = true;
    }
}
private static void BeforeClearFields(object sender, BeforeClearGroupFieldEventArgs args)
{
    if (!args.HasMappedGroupInDataSource)
    {
        //Gets the Current unmerged group name from the event argument
        string[] groupName = args.GroupName.Split(':');
        if (groupName[groupName.Length - 1] == "Orders")
        {
            //Gets the field names in the group
            string[] fields = args.FieldNames;
            List<OrderDetails> orderList = GetOrders();
            //Binds the data to the unmerged fields in group as alternative values
            args.AlternateValues = orderList;
        }
        else
            //If group value is empty, you can set whether the unmerged merge group field can be clear or not
            args.ClearGroup = true;
    }
}
Private Sub BeforeClearFields(ByVal sender As Object, ByVal args As BeforeClearGroupFieldEventArgs)
    If Not args.HasMappedGroupInDataSource Then
        ‘Gets the Current unmerged group name from the event argument
        Dim groupName As String() = args.GroupName.Split(":"c)
        If groupName(groupName.Length - 1) = "Orders" Then
            'Gets the field names in the group
            Dim fields As String() = args.FieldNames
            Dim orderList As List(Of OrderDetails) = GetOrders()
            ‘Binds the data to the unmerged fields in group as alternative values
            args.AlternateValues = orderList
        Else
            ‘If group value is empty, you can set whether the unmerged merge group field can be clear or not
            args.ClearGroup = True
        End If
    End If
End Sub

The following code example shows GetOrders and GetEmployees methods which are used to get data for mail merge.

//Gets order list
private static List<OrderDetails> GetOrders()
{
    List<OrderDetails> orders = new List<OrderDetails>();
    orders.Add(new OrderDetails("10952", new DateTime(2015, 2, 5), new DateTime(2015, 2, 12), new DateTime(2015, 2, 21)));
    return orders;
}

//Gets employee list
public static List<Employees> GetEmployees()
{
    List<OrderDetails> orders = new List<OrderDetails>();
    orders.Add(new OrderDetails("10835", new DateTime(2015, 1, 5), new DateTime(2015, 1, 12), new DateTime(2015, 1, 21)));
    List<CustomerDetails> customerDetails = new List<CustomerDetails>();
    customerDetails.Add(new CustomerDetails("Maria Anders", "Maria Anders", "Berlin", "Germany", orders));
    customerDetails.Add(new CustomerDetails("Andy", "Bernard", "Berlin", "Germany", null));
    List<Employees> employees = new List<Employees>();
    employees.Add(new Employees("Nancy", "Smith", "1", "505 - 20th Ave. E. Apt. 2A,", "Seattle", "USA", customerDetails));
    return employees;
}
//Gets order list
private static List<OrderDetails> GetOrders()
{
    List<OrderDetails> orders = new List<OrderDetails>();
    orders.Add(new OrderDetails("10952", new DateTime(2015, 2, 5), new DateTime(2015, 2, 12), new DateTime(2015, 2, 21)));
    return orders;
}

//Gets employee list
public static List<Employees> GetEmployees()
{
    List<OrderDetails> orders = new List<OrderDetails>();
    orders.Add(new OrderDetails("10835", new DateTime(2015, 1, 5), new DateTime(2015, 1, 12), new DateTime(2015, 1, 21)));
    List<CustomerDetails> customerDetails = new List<CustomerDetails>();
    customerDetails.Add(new CustomerDetails("Maria Anders", "Maria Anders", "Berlin", "Germany", orders));
    customerDetails.Add(new CustomerDetails("Andy", "Bernard", "Berlin", "Germany", null));
    List<Employees> employees = new List<Employees>();
    employees.Add(new Employees("Nancy", "Smith", "1", "505 - 20th Ave. E. Apt. 2A,", "Seattle", "USA", customerDetails));
    return employees;
}
'Gets orders list
Private Shared Function GetOrders() As List(Of OrderDetails)
    Dim orders As List(Of OrderDetails) = New List(Of OrderDetails)()
    orders.Add(New OrderDetails("10835", New DateTime(2015, 1, 5), New DateTime(2015, 1, 12), New DateTime(2015, 1, 21)))
    Return orders
End Function

'Gets employee list
Public Shared Function GetEmployees() As List(Of Employees)
    Dim orders As List(Of OrderDetails) = New List(Of OrderDetails)()
    orders.Add(New OrderDetails("10835", New DateTime(2015, 1, 5), New DateTime(2015, 1, 12), New DateTime(2015, 1, 21)))
    Dim customerDetails As List(Of CustomerDetails) = New List(Of CustomerDetails)()
    customerDetails.Add(New CustomerDetails("Maria Anders", "Maria Anders", "Berlin", "Germany", orders))
    customerDetails.Add(New CustomerDetails("Andy", "Bernard", "Berlin", "Germany", Nothing))
    Dim employees As List(Of Employees) = New List(Of Employees)()
    employees.Add(New Employees("Nancy", "Smith", "1", "505 - 20th Ave. E. Apt. 2A,", "Seattle", "USA", customerDetails))
    Return employees
End Function

The following code example shows Employees, CustomerDetails, and OrderDetails classes.

public class Employees
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string EmployeeID { get; set; }
    public string Address { get; set; }
    public string City { get; set; }
    public string Country { get; set; }
    public List<CustomerDetails> Customers { get; set; }
    public Employees(string firstName, string lastName, string employeeId, string address, string city, string country, List<CustomerDetails> customers)
    {
        FirstName = firstName;
        LastName = lastName;
        Address = address;
        EmployeeID = employeeId;
        City = city;
        Country = country;
        Customers = customers;
    }
}

public class CustomerDetails
{
    public string ContactName { get; set; }
    public string CompanyName { get; set; }
    public string City { get; set; }
    public string Country { get; set; }
    public List<OrderDetails> Orders { get; set; }
    public CustomerDetails(string contactName, string companyName, string city, string country, List<OrderDetails> orders)
    {
        ContactName = contactName;
        CompanyName = companyName;
        City = city;
        Country = country;
        Orders = orders;
    }
}

public class OrderDetails
{
    public string OrderID { get; set; }
    public DateTime OrderDate { get; set; }
    public DateTime ShippedDate { get; set; }
    public DateTime RequiredDate { get; set; }
    public OrderDetails(string orderId, DateTime orderDate, DateTime shippedDate, DateTime requiredDate)
    {
        OrderID = orderId;
        OrderDate = orderDate;
        ShippedDate = shippedDate;
        RequiredDate = requiredDate;
    }
}
public class Employees
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string EmployeeID { get; set; }
    public string Address { get; set; }
    public string City { get; set; }
    public string Country { get; set; }
    public List<CustomerDetails> Customers { get; set; }
    public Employees(string firstName, string lastName, string employeeId, string address, string city, string country, List<CustomerDetails> customers)
    {
        FirstName = firstName;
        LastName = lastName;
        Address = address;
        EmployeeID = employeeId;
        City = city;
        Country = country;
        Customers = customers;
    }
}

public class CustomerDetails
{
    public string ContactName { get; set; }
    public string CompanyName { get; set; }
    public string City { get; set; }
    public string Country { get; set; }
    public List<OrderDetails> Orders { get; set; }
    public CustomerDetails(string contactName, string companyName, string city, string country, List<OrderDetails> orders)
    {
        ContactName = contactName;
        CompanyName = companyName;
        City = city;
        Country = country;
        Orders = orders;
    }
}

public class OrderDetails
{
    public string OrderID { get; set; }
    public DateTime OrderDate { get; set; }
    public DateTime ShippedDate { get; set; }
    public DateTime RequiredDate { get; set; }
    public OrderDetails(string orderId, DateTime orderDate, DateTime shippedDate, DateTime requiredDate)
    {
        OrderID = orderId;
        OrderDate = orderDate;
        ShippedDate = shippedDate;
        RequiredDate = requiredDate;
    }
}
Public Class Employees
    Public Property FirstName As String
    Public Property LastName As String
    Public Property EmployeeID As String
    Public Property Address As String
    Public Property City As String
    Public Property Country As String
    Public Property Customers As List(Of CustomerDetails)
    Public Sub New(ByVal firstName As String, ByVal lastName As String, ByVal employeeId As String, ByVal address As String, ByVal city As String, ByVal country As String, ByVal customers As List(Of CustomerDetails))
        Me.FirstName = firstName
        Me.LastName = lastName
        Me.Address = address
        Me.EmployeeID = employeeId
        Me.City = city
        Me.Country = country
        Me.Customers = customers
    End Sub
End Class

Public Class CustomerDetails
    Public Property ContactName As String
    Public Property CompanyName As String
    Public Property City As String
    Public Property Country As String
    Public Property Orders As List(Of OrderDetails)
    Public Sub New(ByVal contactName As String, ByVal companyName As String, ByVal city As String, ByVal country As String, ByVal orders As List(Of OrderDetails))
        Me.ContactName = contactName
        Me.CompanyName = companyName
        Me.City = city
        Me.Country = country
        Me.Orders = orders
    End Sub
End Class

Public Class OrderDetails
    Public Property OrderID As String
    Public Property OrderDate As DateTime
    Public Property ShippedDate As DateTime
    Public Property RequiredDate As DateTime
    Public Sub New(ByVal orderId As String, ByVal orderDate As DateTime, ByVal shippedDate As DateTime, ByVal requiredDate As DateTime)
        Me.OrderID = orderId
        Me.OrderDate = orderDate
        Me.ShippedDate = shippedDate
        Me.RequiredDate = requiredDate
    End Sub
End Class

You can download a complete working sample from GitHub.

See Also