How To add an attribute to an HTML element and change its value at run-time?

You can add an attribute to an HTML element using the Add method of the Attributes property, as shown in the following code snippet.

// textBox is an INPUT element of type 'text' in the HTML document

if(this.textBox.Attributes.Contains("style") == false)

this.textBox.Attributes.Add("style");
' textBox is an INPUT element of type 'text' in the HTML document

If Me.textBox.Attributes.Contains("style") = False Then

Me.textBox.Attributes.Add("style")

End If

You can change the value of an element’s attribute at run time by using the Value property of that particular attribute, as shown in the below code snippet.

// textBox is an INPUT element of type 'text' in the HTML document

this.textBox.Attributes["style"].Value = "background-color:red";
' textBox is an INPUT element of type 'text' in the HTML document

Private Me.textBox.Attributes("style").Value = "background-color:red"