Class DropDownListEvents<TValue, TItem>

Defines the events for the SfDropDownList<TValue, TItem> component.

Inheritance

System.Object

DropDownListEvents<TValue, TItem>

Namespace: Syncfusion.Blazor.DropDowns

Assembly: Syncfusion.Blazor.dll

Syntax

public class DropDownListEvents<TValue, TItem> : OwningComponentBase

Type Parameters

Name	Description
TValue	The type of the value selected in the SfDropDownList<TValue, TItem>.
TItem	The type of items displayed in the dropdown list.

Remarks

This class provides event callbacks for various interactions with the SfDropDownList<TValue, TItem> component, such as data fetching, popup actions, and value changes.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" ValueChange="@OnChange" OnOpen="@OnOpenHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnChange(ChangeEventArgs<string, string> args)
    {
        // Handle value change
    }
    public void OnOpenHandler(BeforeOpenEventArgs args)
    {
        args.Cancel = true; // Prevent popup from opening
    }
}

Constructors

DropDownListEvents()

Declaration

public DropDownListEvents()

Properties

BaseParent

Specifies the base parent of the component.

Declaration

protected SfDropDownList<TValue, TItem> BaseParent { get; set; }

Property Value

Type
SfDropDownList<TValue, TItem>

Blur

Gets or sets the event callback invoked when the dropdown loses focus.

Declaration

public EventCallback<object> Blur { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<System.Object>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an System.Object when triggered.

Remarks

This event is triggered when the SfDropDownList<TValue, TItem> component loses focus, allowing developers to perform actions such as UI updates or validation checks.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" Blur="@OnBlurHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnBlurHandler(object args)
    {
        // Handle blur event
    }
}

Closed

Gets or sets the event callback invoked after the dropdown popup has closed.

Declaration

public EventCallback<ClosedEventArgs> Closed { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<ClosedEventArgs>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a ClosedEventArgs object when triggered.

Remarks

This event is triggered after the dropdown popup is closed, allowing developers to perform post-closure actions such as updating the UI or processing the selected value.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" Closed="@OnClosedHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnClosedHandler(ClosedEventArgs args)
    {
        // Handle popup closed event
    }
}

Created

Gets or sets the event callback invoked when the component is created.

Declaration

public EventCallback<object> Created { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<System.Object>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an System.Object when triggered.

Remarks

This event is triggered when the SfDropDownList<TValue, TItem> component is initialized and rendered, allowing developers to perform setup tasks or initialization logic.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" Created="@OnCreatedHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnCreatedHandler(object args)
    {
        Console.WriteLine("DropDownList created.");
    }
}

DataBound

Gets or sets the event callback invoked when the data source is populated in the popup list.

Declaration

public EventCallback<DataBoundEventArgs> DataBound { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<DataBoundEventArgs>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a DataBoundEventArgs object when triggered.

Remarks

This event is triggered after the data source is populated in the dropdown popup, providing access to the populated items via Items. It is useful for post-processing or validating the data displayed in the popup.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" DataBound="@OnDataBoundHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnDataBoundHandler(DataBoundEventArgs args)
    {
        // Process populated data
    }
}

Destroyed

Gets or sets the event callback invoked when the component is destroyed.

Declaration

public EventCallback<object> Destroyed { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<System.Object>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an System.Object when triggered.

Remarks

This event is triggered when the SfDropDownList<TValue, TItem> component is disposed, allowing developers to perform cleanup tasks or release resources.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" Destroyed="@OnDestroyedHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnDestroyedHandler(object args)
    {
        Console.WriteLine("DropDownList destroyed.");
    }
}

Filtering

Gets or sets the event callback invoked when a character is typed in the filter textbox.

Declaration

public EventCallback<FilteringEventArgs> Filtering { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<FilteringEventArgs>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a FilteringEventArgs object when triggered.

Remarks

This event is triggered when the user types in the filter textbox and AllowFiltering is enabled. Developers can prevent the default filtering action using PreventDefaultAction and customize the filtering logic by passing a modified query to the FilterAsync method.

Examples

<SfDropDownList @ref="DDLObj" TItem="string" TValue="string" AllowFiltering="true" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" Filtering="@OnFilteringHandler"/>
</SfDropDownList>
@code {
    SfDropDownList<string, string> DDLObj { get; set; }
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public async Task OnFilteringHandler(FilteringEventArgs args)
    {
        args.PreventDefaultAction = true;
        var query = new Query().Where(new WhereFilter { Field = "Text", Operator = "contains", value = args.Text, IgnoreCase = true });
        await DDLObj.FilterAsync(MyList, query);
    }
}

Focus

Gets or sets the event callback invoked when the component gains focus.

Declaration

public EventCallback<object> Focus { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<System.Object>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an System.Object when triggered.

Remarks

This event is triggered when the SfDropDownList<TValue, TItem> component gains focus, allowing developers to perform actions such as UI updates or input preparation.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" Focus="@OnFocusHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnFocusHandler(object args)
    {
        Console.WriteLine("DropDownList gained focus.");
    }
}

OnActionBegin

Gets or sets the event callback invoked before fetching data from the data source.

Declaration

public EventCallback<ActionBeginEventArgs> OnActionBegin { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<ActionBeginEventArgs>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an ActionBeginEventArgs object when triggered.

Remarks

This event is triggered before the data fetch operation starts, allowing developers to modify the query or cancel the operation using Cancel. It is useful for initializing or customizing data retrieval logic.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnActionBegin="@OnActionBeginHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnActionBeginHandler(ActionBeginEventArgs args)
    {
        args.Cancel = true; // Cancel data fetch
    }
}

OnActionComplete

Gets or sets the event callback invoked after data is successfully fetched from the data source.

Declaration

public EventCallback<ActionCompleteEventArgs<TItem>> OnActionComplete { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<ActionCompleteEventArgs<TItem>>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an ActionCompleteEventArgs<TItem> object when triggered.

Remarks

This event is triggered after the data fetch operation completes successfully, providing access to the fetched data via Result. Developers can use this event to process or modify the data before it is displayed in the dropdown.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnActionComplete="@OnActionCompleteHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnActionCompleteHandler(ActionCompleteEventArgs<string> args)
    {
        // Process fetched data
    }
}

OnActionFailure

Gets or sets the event callback invoked when the data fetch request fails.

Declaration

public EventCallback<Exception> OnActionFailure { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<System.Exception>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an System.Exception object when triggered.

Remarks

This event is triggered when a data fetch operation fails, providing the exception details for error handling or logging purposes. Developers can use this event to display error messages or implement fallback logic.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnActionFailure="@OnActionFailureHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnActionFailureHandler(Exception ex)
    {
        Console.WriteLine($"Data fetch failed: {ex.Message}");
    }
}

OnClose

Gets or sets the event callback invoked before the dropdown popup closes.

Declaration

public EventCallback<PopupEventArgs> OnClose { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<PopupEventArgs>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a PopupEventArgs object when triggered.

Remarks

This event is triggered before the dropdown popup closes, allowing developers to cancel the action using Cancel. If cancelled, the popup remains open, enabling custom control over the closing behavior.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnClose="@OnCloseHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnCloseHandler(PopupEventArgs args)
    {
        args.Cancel = true; // Prevent popup from closing
    }
}

OnOpen

Gets or sets the event callback invoked before the dropdown popup opens.

Declaration

public EventCallback<BeforeOpenEventArgs> OnOpen { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<BeforeOpenEventArgs>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a BeforeOpenEventArgs object when triggered.

Remarks

This event is triggered before the dropdown popup opens, allowing developers to cancel the action using Cancel. It is useful for validating conditions or modifying the popup behavior before it is displayed.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnOpen="@OnOpenHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnOpenHandler(BeforeOpenEventArgs args)
    {
        args.Cancel = true; // Prevent popup from opening
    }
}

OnResizeStart

Gets or sets the event callback invoked when the popup resizing action begins.

Declaration

public EventCallback<object> OnResizeStart { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<System.Object>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an System.Object containing resize start data when triggered.

Remarks

This event is triggered when the user starts resizing the dropdown popup, provided AllowResize is enabled. It is useful for initializing states, logging, or displaying messages during the resizing process.

Examples

<SfDropDownList TItem="string" TValue="string" AllowResize="true" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnResizeStart="@HandleResizeStart"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void HandleResizeStart(object args)
    {
        Console.WriteLine("Resizing has started.");
    }
}

OnResizeStop

Gets or sets the event callback invoked when the popup resizing action is completed.

Declaration

public EventCallback<object> OnResizeStop { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<System.Object>	An Microsoft.AspNetCore.Components.EventCallback<> that receives an System.Object containing resize stop data when triggered.

Remarks

This event is triggered when the user finishes resizing the dropdown popup, provided AllowResize is enabled. It is ideal for finalizing layout adjustments, saving the final size, or logging the resize completion.

Examples

<SfDropDownList TItem="string" TValue="string" AllowResize="true" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnResizeStop="@HandleResizeStop"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void HandleResizeStop(object args)
    {
        Console.WriteLine("Resizing has stopped.");
    }
}

OnValueSelect

Gets or sets the event callback invoked when an item is selected from the dropdown popup.

Declaration

public EventCallback<SelectEventArgs<TItem>> OnValueSelect { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<SelectEventArgs<TItem>>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a SelectEventArgs<T> object when triggered.

Remarks

This event is triggered when an item is selected from the dropdown popup via mouse, tap, or keyboard navigation. Developers can prevent the selection using Cancel and access the selected item via ItemData.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" OnValueSelect="@OnSelectHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnSelectHandler(SelectEventArgs<string> args)
    {
        if (args.ItemData == "Medium")
            args.Cancel = true; // Prevent selection
    }
}

Opened

Gets or sets the event callback invoked when the dropdown popup opens.

Declaration

public EventCallback<PopupEventArgs> Opened { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<PopupEventArgs>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a PopupEventArgs object when triggered.

Remarks

This event is triggered after the dropdown popup is opened, providing access to popup properties via Popup for further customization or interaction.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" Opened="@OnOpenedHandler"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnOpenedHandler(PopupEventArgs args)
    {
        // Handle popup opened event
    }
}

ValueChange

Gets or sets the event callback invoked when the Value property changes.

Declaration

public EventCallback<ChangeEventArgs<TValue, TItem>> ValueChange { get; set; }

Property Value

Type	Description
Microsoft.AspNetCore.Components.EventCallback<ChangeEventArgs<TValue, TItem>>	An Microsoft.AspNetCore.Components.EventCallback<> that receives a ChangeEventArgs<TValue, TItem> object when triggered.

Remarks

This event is triggered when an item is selected from the dropdown popup or when the value is changed programmatically. It provides details about the new and previous values, allowing developers to respond to value changes.

Examples

<SfDropDownList TItem="string" TValue="string" DataSource="@MyList">
    <DropDownListEvents TValue="string" TItem="string" ValueChange="@OnChange"/>
</SfDropDownList>
@code {
    protected List<string> MyList = new List<string> { "Small", "Medium", "Large" };
    public void OnChange(ChangeEventArgs<string, string> args)
    {
        var selectedValue = args.Value;
    }
}

Methods

ComponentDispose(Boolean)

Declaration

protected void ComponentDispose(bool disposing)

Parameters

Type	Name	Description
System.Boolean	disposing