Is there any benefit to use the sender parameter instead of direct access to required control

Question

Is there any situation when I should prefer to use the sender parameter of the controls' event handlers instead of the direct access to required control?

So instead of

    private void okButton_Click(object sender, EventArgs e)
    {
      okButton.Enabled = false;
    }

I should use

    private void okButton_Click(object sender, EventArgs e)
    {
      (sender as Button).Enabled = false;
    }

Is there any benefit at all?

Answer 1

As LarsTech indicated in comment, if you have multiple "Clicks" being handled by the same function, using sender can be advantageous to prevent duplicate code.

Terrible example, but if you have:

<asp:Button ID="Button1" runat="server" Text="Not Clicked" OnClick="Button_Click" />
<asp:Button ID="Button2" runat="server" Text="Not Clicked" OnClick="Button_Click" />
<asp:Button ID="Button3" runat="server" Text="Not Clicked" OnClick="Button_Click" />

Your handler:

protected void Button_Click(object sender, EventArgs e)
{
  (sender as Button).Text = "Totes clicked";
}

vs having 3 handlers that do the same thing, but for each individual button.

Additionally, when working with controls within repeaters or within a datagrid , you wouldn't necessarily be able to access your control by its name directly, in instances like this sender can be a more attractive option over trying to cast it by row index.

Answer 2

The main use is when you use one handler method to handle event of multiple objects. This way you can concentrate your code in one central method.

Another usage is when you creates controls at runtime and assign event handler to them. In such cases you must use this method.

Somewhere attach a handler to event of your controls.

this.NewToolStripButton.Click += new System.EventHandler(this.ToolStripButton_Click);
this.EditToolStripButton.Click += new System.EventHandler(this.ToolStripButton_Click);
this.DeleteToolStripButton.Click += new System.EventHandler(this.ToolStripButton_Click);
this.DetailsToolStripButton.Click += new System.EventHandler(this.ToolStripButton_Click);

Thene use it this way:

private void ToolStripButton_Click(object sender, EventArgs e)
{
    var toolstripItem = sender as ToolStripItem;
    if (toolstripItem == null)
        return;

    switch(toolstripItem.Name)
    {
        case "NewToolStripItem":
            //Do New stuff here
            break;
        case "EditToolStripItem":
            //Do Edit stuff here
            break;
        case "DeleteToolStripItem":
            //Do Delete stuff here
            break;
        case "DetailsToolStripItem":
            //Do Details stuff here
            break;
        default:
            break;
    }
}