asp:button Created Programmatically: EventHandler does not fire

Question

I am writing a SharePoint web part which will have a simple ASP.NET form. I am using HtmlTextWriter to render the controls. The problem I have is that my button does not seem to be triggering the EventHandler I have assigned it.

I initially declared the button in the CreateChildControls method, and wired the event handler:

    {
        Button submitButton;
        submitButton = new Button();
        submitButton.Text = "Go!";
        submitButton.Click += new EventHandler(submitButton_Click);
        Controls.Add(submitButton);
    }

I have declared the functionality of the "submitButton_Click" EventHandler:

    void submitButton_Click(object sender, EventArgs e)
    {
        submitButton.Text = "Good!";
    }

I render the controls:

protected override void RenderContents(System.Web.UI.HtmlTextWriter output)
{ 
        RenderChildren(output);
}

Finally, I deploy the web part. It shows up fine in the catalog and when I add it to a page, the control shows up. However, I would assume that when I click the button, its text should change from "Go!" to "Good!" Instead, it does nothing. I'm pretty new to all of these technologies -- C#, Sharepoint, and ASP.NET -- so I'm pretty sure it's a problem with my understanding, but trying different steps from articles all over the net and previous questions here haven't fixed my problem. Thanks for taking a look.

EDIT: I opened the SharePoint page with the web part on it and the button has been created like so:

<input type="submit" name="ctl00$PlaceHolderMain$ctl00$ctl04" value="Go!" />

It looks like the OnClick value has not been added at all, which is what I thought adding the EventHandler would do. Am I trying to add OnClick in a completely wrong way? I also don't understand why the button name does not match what I declared in my code.

Answer 1

Look at this link:

http://msdn.microsoft.com/en-us/library/ms452873.aspx

You're overriding the RenderContents method incorrectly, and wiring the click event in the wrong place.

Answer 2

Use the CreateChildControls override instead, this gets called at the right moment in the ASP.NET Control rendering pipeline.

Answer 3

Are you inheriting from System.Web.UI.WebControls.WebParts.WebPart or the SharePoint WebPart (Sorry, I don't recall the namespace). It is recommended to inherit from "System.Web.UI.WebControls.WebParts.WebPart" so that it is a simple ASP.NET Web Part and it can also be used in SharePoint.

Once you inherit from that class, you will need to override the "Render" method which is what I always do and it works out fine. I think your CreatechildControls method is correct. So your Render method will look like

protected override void Render(System.Web.UI.HtmlTextWriter output)
{ 
        submitButton.RenderControl(write);
}

You will also need to declare your button outside the "CreateChildControls" method.When writing SharePoint WebParts, I always take this approach

1. Inherit from System.Web.UI.WebControls.WebParts.WebPart
2. Create a partial class which will be used to declare all the controls used by the WebPart and to override the following methods: "CreateChildControls", "OnInit", and "Render".

Hope it helps.

Answer 4

I had a similar problem. The event handler was always firing. I checked the view source of the SharePoint page and discovered the HTML control rendered was the input type = submit. To solve the issue, I set the 'button.UseSubmitBehavior = false' in code and set the ID. UseSubmitBehavior by default in ASP.NET 2.0 is true, if not set in code.