Webparts in MOSS 2007 - Part 2

In the first part, we talked about creating the simplest of WebPart and the classes of concern. This time, lets render something meaningfull in our webpart. How about the list of all the users in the system ? We would be using the MOSS libraries to get this information.

Steps
As usual, create a blank class derived from System.Web.UI.WebControls.WebParts.WebPart and override the render method as :

protected override void Render(HtmlTextWriter writer)
{
  writer.Write(GetHTML());
}

private string GetHTML()
{
  string result = "<table border=\"0\">";
  try
  {
    ServerContext context = ServerContext.GetContext(Context);
    UserProfileManager profileManager = new UserProfileManager(context);
    foreach (UserProfile profile in profileManager)
    {
      if (profile.PublicUrl.AbsoluteUri != null)
      {
        result += "<tr><td><a href=\"" + SPEncode.HtmlEncode(profile.PublicUrl.AbsoluteUri) + "\"/>" +
              SPEncode.HtmlEncode(profile[PropertyConstants.AccountName].ToString()) + "</a></td></tr>";
      }
    }
    result += "</table>";
  }
  catch (Exception ex)
  {
    result += "<tr><td>" + ex.ToString() + "</td></tr></table>";             
  }
  return result;
}

As seen, the GetHTML function returns the HTML string which needs to be rendered at the Render() function. GetHTML uses the server context together with the UserProfileManager to get all the user profiles in the Sharepoint system. In addition to this, we have rendered a link for each of the user such that it takes you to the home page of the user.

You would need to include the following namespaces in the 'using' section if not already done : Microsoft.Office.Server, Microsoft.Office.Server.UserProfiles, Microsoft.SharePoint.Utilities, Microsoft.SharePoint.

Follow the either of the two steps mentioned in the previous post to register this webpart on the server and test it out.

More rendering with data from the DB

Lets create another WebPart which renders data from the DB onto a DataGrid. The core idea remains the same. You perform the render on the items that you know and for your child controls (DataGrid, Label etc), you ask them to render themselves.The crux of the code is contained in the following :

protected override void Render(HtmlTextWriter writer)
{
  EnsureChildControls(); //makes sure the child control were created

  LoadData();

  writer.RenderBeginTag("table");

  writer.RenderBeginTag("tr");
  writer.RenderBeginTag("td");
  lblSubmit.RenderControl(writer);
  writer.RenderEndTag();
  writer.RenderEndTag();

  writer.RenderBeginTag("tr");
  writer.RenderBeginTag("td");
  gridProductList.RenderControl(writer);
  writer.RenderEndTag();
  writer.RenderEndTag();

  writer.RenderEndTag(); //end table
}

protected override void CreateChildControls()
{
  base.CreateChildControls();

  lblSubmit = new Label();
  lblSubmit.Text = "Employee List";
  Controls.Add(lblSubmit);

  gridProductList = new DataGrid();
  Controls.Add(gridProductList);
}

Note the usage of RenderBeginTag and RenderEndTag which generates the matching start and end tags. Within each of the tags, we render the specific control. As seen, the DataGrid (gridProductList) gets rendered in the appropriate table column within a html row.

LoadData() function referred in Render() basically loads the data into the DataGrid using standard data access calls. Any child control the webpart uses should desirably be created at the CreateChildControls method. Though we might as well do this when the WebPart gets created, writing it here ensures that EnsureChildControls() call it when required.

I hope this gives you a gist of how WebParts are created and used. In the next parts, we shall see about Custom Editors and inter WebPart communication.