I need to trigger code on the server side to be called when a TextBox loses focus.
I know there is the onblur client side event, and that there is no LostFocus event, so how can I cause a postback to occur when my TextBox loses focus?
Update:
I have found a blog which seems to give a pretty decent solution to this. It involves adding a custom event to a TextBox subclass, and registering a client script which calls the server-side event in the onblur JavaScript client event.
The following is my implementation in VB:
Public Class MyTextBox
Inherits TextBox
Implements IPostBackEventHandler
Protected Overrides Sub OnInit(ByVal e As System.EventArgs)
MyBase.OnInit(e)
If Not Page.ClientScript.IsClientScriptBlockRegistered("OnBlurTextBoxEvent") Then
Page.ClientScript.RegisterStartupScript(MyBase.GetType, "OnBlurTextBoxEvent", GetScript, True)
Attributes.Add("onblur", "OnBlurred('" & UniqueID & "','')")
End If
End Sub
Public Delegate Sub OnBlurDelegate(ByVal sender As Object, ByVal e As EventArgs)
Public Event Blur As OnBlurDelegate
Protected Sub OnBlur()
RaiseEvent Blur(Me, EventArgs.Empty)
End Sub
Private Function GetScript() As String
Return "function OnBlurred(control, arg)" & vbCrLf & _
"{" & vbCrLf & _
" __doPostBack(control, arg);" & vbCrLf & _
"}"
End Function
Public Sub RaisePostBackEvent(ByVal eventArgument As String) Implements System.Web.UI.IPostBackEventHandler.RaisePostBackEvent
OnBlur()
End Sub
End Class