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Errorhandling in Webparts for SharePoint 2007

, 11 Apr 2007
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An approach for handling errors in webparts for SharePoint 2007

Introduction

When delivering webparts you need to have an approach on how to handle errors so that the the webpart "dies" in a nice way and can also communicate the problem to the administrators in a controlled way. This article explains the approach I have used. The approach used here is to catch the error in CreateChildControl and then display the error during the rendering in LiteralControls.

Webpart overrides

If you inherit from System.Web.UI.WebControls.WebParts.Webpart you should override the following methods:

  1. CreateChildControls: called by the ASP.NET page Framework to notify server controls that use composition-based implementation to create any child controls that they contain in preparation for posting back or rendering.
  2. Render: renders the control to the specified HTML writer.

Who should catch what we throw...

The problem I have seen is that if you don't handle errors in a controlled way, the whole SharePoint page gets corrupt which is not acceptable. We should have the following goals of how we handle errors:

  1. Die in a graceful way
    If a webpart just throws an error, the Sharepoint page is not usable
  2. Report something back to the end user
    We need to tell the end user that we have a problem
  3. Send more error information for troubleshooting
    We need to have the possibility to have more extensive error reporting for the System Administrator...

My Approach: Coding a webpart

To at least "die" in a controlled way, I have implemented the following approach. I am still missing some good guidelines on how to do Tracing and Event logging inside Sharepoint 2007 from Microsoft.

  1. Create a private variable to store the Exception inside the webpart
    private Exception childException = null;
  2. In CreateChildControls, have a try/catch and catch the error in the childException variable
    try
    {
        base.CreateChildControls();
        .....
    }
    catch (Exception exp)
    {
        HttpContext ctx = HttpContext.Current;
        ctx.Trace.Warn(ex.ToString());
        childException = ex;
    }
    
  3. In Render check using try/catch and catch the error in the childException variable and then display the result in the page by using labels..
    protected override void Render(System.Web.UI.HtmlTextWriter writer)
    {
        if (childException != null)
        displayErrorMsg(writer, childException);
        try
        {
            ...
            ...
            ...
        }
        catch (Exception ex)
        {
            displayErrorMsg(writer, ex);
        }
    

    where

    private void displayErrorMsg(HtmlTextWriter writer, Exception ex)
    {
        this.Controls.Clear();
        this.Controls.Add(new LiteralControl(ex.Message));
        if (ex.InnerException != null)
        {
            this.Controls.Add(new LiteralControl(ex.InnerException.Message));
        }
        this.Controls.Add(new LiteralControl());
        base.Render(writer);
        HttpContext ctx = HttpContext.Current;
        ctx.Trace.Warn(ex.ToString());
    }
    

Points of Interest

After working with SharePoint 2007, I miss good information sources regarding creating webparts. Most examples are just of the "Hello World" complexity which is useless if you would like to deliver something for production.

History

  • 11th April, 2007: Created

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Magnus Salgo
Web Developer
Denmark Denmark
Run my own consulting company in Stockholm, Sweden and deliver solutions using C#, .NET, Sharepoint 2007, Microsoft Project Server.
 
I have also been working with document managment software as Livelink from Open Text, BASISplus from Information Dimensions.
 
My bio Magnus Sälgö, Sweden
MSN: salgo60@msn.com
Skype: salgo60

Comments and Discussions

 
GeneralMy vote of 4 Pinmemberdavedfq11-Oct-11 10:35 
GeneralOverly Simplistic Pinmemberozcro16-Apr-07 22:59 
GeneralRe: Overly Simplistic PinmemberMagnus Salgo17-Apr-07 1:01 
GeneralRe: Overly Simplistic PinmemberMagnus Salgo17-Apr-07 23:13 
GeneralMore about error handling in Sharepoint PinmemberMagnus Salgo2-Feb-08 1:44 
GeneralRe: Overly Simplistic Pinmemberozcro7-May-07 22:49 
GeneralJ2EE/Java app with Sharepoint Pinmembervikram Verma11-Apr-07 23:16 
GeneralRe: J2EE/Java app with Sharepoint PinmemberMagnus Salgo12-Apr-07 0:06 

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