Calling client methods

Several client methods accomplish the same tasks as actions of Button controls. If your DataWindow object uses Button controls to implement scrolling and updating, you might not need to do any client scripting.

You can use the methods in the first column in Table 12-2 on the client in client-side events or functions. Methods marked with an asterisk force the Web page to be reloaded. The second column lists the properties and methods that perform the same function in a DataWindowControl or the server WebDataWindowControl.

For a description of each client method, see “Alphabetical list of methods for the Web DataWindow client control”. For a description of the properties and methods in the second column, see the Sybase DataWindow help in Visual Studio.

This function in the script area of a Web form’s .aspx page updates data:

function btnUpdate_onclick() {
   objdwCustomer.Update();
}

The button is defined in the form:

<form id = "Form1" method="post" runat="server">
   <INPUT language="javascript" id="btnUpdate"
      type="button" value="Update" 
      onClick="return btnUpdate_onclick">
   ...
</form>

Note that you can get the same functionality with the Update action for a Button control in the DataWindow object. For more information, see “Using Button and Picture controls”.

Handling method failures

The methods marked with an asterisk in Table 12-2 cause an action to be posted back to the server. Whenever an action is posted back to the server, the server-side BeforePerformAction event is fired before the action is performed, enabling the user to cancel the action, and the AfterPerformAction event is fired after the action is performed.

These methods always return 1 unless the AcceptText method that is called implicitly after each method is called fails. Use the AfterPerformAction event to test whether the action was performed successfully. The AfterPerformAction event handler has two arguments. The Action argument indicates the type of the postback action, for example ScrollNextPage, InsertRow, or Retrieve. These actions can be posted from buttons in the DataWindow object as well as from client script. The ActionResult argument indicates whether the action succeeded.

The following example in the code file for a form writes the result of an action to a text box called txtMsg:

[Visual Basic]
Private Sub dw1_AfterPerformAction(ByVal sender As  _
   Object, ByVal e As   _
   Sybase.DataWindow.Web.AfterPerformActionEventArgs)_
   Handles dw1.AfterPerformAction

   txtMsg.Text = "AfterPerformAction: " +  _
     e.Action.ToString + " " + e.ActionResult.ToString
End Sub

[C#]
private void wdw_afteraction(object sender, Sybase.DataWindow.Web.AfterPerformActionEventArgs e)
{
   this.txtMsg.Text = this.txtMsg.Text +
      "AfterPerformAction: " + e.Action.ToString() + 
      " " + e.ActionResult.ToString();
}

Note that client-side methods do not throw DbErrorExceptions, so you might choose to use server-side methods to obtain better information about database errors.

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