Chapter 16: Checking Roles with IsUserInRole at Run Time

phztfte1 · January 18th, 2016, 09:42 PM

Hi Imar,

I got the yellow screen of death for the last Try It Out in Chapter 16. Here's is the output:

Code:

Server Error in '/' Application.
________________________________________
Object reference not set to an instance of an object. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 

Line 79:         case ListViewItemType.DataItem:
Line 80:           Button deleteButton = (Button)e.Item.FindControl("DeleteButtom");
Line 81:           deleteButton.Visible = Roles.IsUserInRole("Managers");
Line 82:           break;
Line 83:       }

Source File: c:\BegASPNET\Site\ManagePhotoAlbum.aspx.cs    Line: 81 

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]
   _ManagePhotoAlbum.ListView1_ItemCreated(Object sender, ListViewItemEventArgs e) in c:\BegASPNET\Site\ManagePhotoAlbum.aspx.cs:81
   System.Web.UI.WebControls.ListView.OnItemCreated(ListViewItemEventArgs e) +91
   System.Web.UI.WebControls.ListView.CreateItemsWithoutGroups(ListViewPagedDataSource dataSource, Boolean dataBinding, InsertItemPosition insertPosition, ArrayList keyArray) +739
   System.Web.UI.WebControls.ListView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding) +1032
   System.Web.UI.WebControls.ListView.PerformDataBinding(IEnumerable data) +35
   System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data) +128
   System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +34
   System.Web.UI.WebControls.ModelDataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +80
   System.Web.UI.WebControls.DataBoundControl.PerformSelect() +143
   System.Web.UI.WebControls.ListView.PerformSelect() +102
   System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +74
   System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +114
   System.Web.UI.WebControls.ListView.CreateChildControls() +52
   System.Web.UI.Control.EnsureChildControls() +92
   System.Web.UI.Control.PreRenderRecursiveInternal() +42
   System.Web.UI.Control.PreRenderRecursiveInternal() +160
   System.Web.UI.Control.PreRenderRecursiveInternal() +160
   System.Web.UI.Control.PreRenderRecursiveInternal() +160
   System.Web.UI.Control.PreRenderRecursiveInternal() +160
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4775


________________________________________
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.1038.0

Please help resolve.

Imar · January 19th, 2016, 03:34 AM

You'll have to debug the code to see what's null exactly and why but my guess is this:

Button deleteButton = (Button)e.Item.FindControl("DeleteButtom");

Your button may have a different name in the UI;l for example DeleteButton with an N instead of DeleteButtom with an M.

Cheers,

Imar

phztfte1 · January 19th, 2016, 09:53 AM

Thanks Imar. The typo was the problem. I haven't gotten the hang of using the debugger. But, I will skip Chapter 17 and move on to Chapter 18.

Thank you again.