System.NullReferenceException: Object reference not set to an instance of an object. - Trying to hide button in details view RSS

• • Reply
  

  funluckykitt...

  Participant

  1470 Points

  1550 Posts

  System.NullReferenceException: Object reference not set to an instance of an object. - Trying to ...

  Nov 09, 2012 05:55 PM|LINK

  I have a detils view on a page, that if a user isn't a "PowerUser", I need to hide the edit button of the detailsview.   But, I keep getting this error.  Object reference not set to an instance of an object.

  Here's my code from my code behind, where I'm checking the access level, and if  the user isn't the proper level, I'm trying to hide the button.  What am I forgeting to do? 
  
  From my page  & Code behind

  <asp:TemplateField HeaderText="">
  <EditItemTemplate>
  <asp:Button ID="btnUpdate" runat="server" CausesValidation="True" CommandName="Update" Text="Update" />
  <asp:Button ID="btnCancel" runat="server" CausesValidation="False" CommandName="Cancel" Text="Cancel" />
  </EditItemTemplate>
  <ItemTemplate>
  <asp:Button ID="btnEdit" runat="server" CausesValidation="False" CommandName="Edit"Text="Edit"/>
  </ItemTemplate>
  </asp:TemplateField>
  
  From my code behind:
  
  protected void dvDetails_DataBound(object sender,  EventArgs e)
     {
         Button btnEdit = (Button)dvDetails.FindControl("btnEdit") as Button;
         
         if (Session["PowerUser"] == "Y")
         {
             btnEdit.Visible = false;
         }
         else
         {
             btnEdit.Visible = true;
         }
  
     }

  --Susan
  • Edited by bbcompent1 on Nov 09, 2012 06:07 PM
• • Reply
  

  bbcompent1

  All-Star

  33718 Points

  8737 Posts

  Moderator

  Re: System.NullReferenceException: Object reference not set to an instance of an object. - Trying...

  Nov 09, 2012 06:07 PM|LINK

  I think the null value is your session variable as you aren't putting it out as a string. I would put the session variable into a string variable and compare that way.

  string CompareVal = Session["PowerUser"];
  if (CompareVal == "Y")
     {

  Mark as answer posts that helped you.
  
• • Reply
  

  funluckykitt...

  Participant

  1470 Points

  1550 Posts

  Re: System.NullReferenceException: Object reference not set to an instance of an object. - Trying...

  Nov 09, 2012 07:54 PM|LINK

  Tried that, but get this error   CS0266: Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists (are you missing a cast?)
  
  

  --Susan
• • Reply
  

  funluckykitt...

  Participant

  1470 Points

  1550 Posts

  Re: System.NullReferenceException: Object reference not set to an instance of an object. - Trying...

  Nov 09, 2012 07:56 PM|LINK

  Forgot to mention, that the line it's failing on is below, so it's fine on the session portion, just not on finding the button from the details view..??

  btnEdit.Visible = true;

  --Susan
• • Reply
  

  clevesteve

  Participant

  1405 Points

  406 Posts

  Re: System.NullReferenceException: Object reference not set to an instance of an object. - Trying...

  Nov 09, 2012 08:39 PM|LINK

  Couple things... from the looks of your code, you are hiding the edit button if the user is a power user... is that what you want to do?

  Also, is the DetailsView definitely in read-only mode?  I'm pretty sure this will fail when the DetailsView is in Edit mode.

  protected void dvDetails_DataBound(object sender,  EventArgs e)
     {
         Button btnEdit = (Button)dvDetails.FindControl("btnEdit") as Button;
         
         If(dvDetails.CurrentMode == DetailsViewMode.ReadOnly)
         {
         if (Session["PowerUser"] == "Y")
         {
             btnEdit.Visible = false;
         }
         else
         {
             btnEdit.Visible = true;
         }
         }
  
     }

  
  
  

  Not an IT Professional
• • Reply
  

  monjurul hab...

  Member

  62 Points

  11 Posts

  Re: System.NullReferenceException: Object reference not set to an instance of an object. - Trying...

  Nov 09, 2012 09:43 PM|LINK

  Steps should follow:

  1) No exception is thrown if you attempt to get a value out of session state that does not exist. To be sure that the value you want is in session state, check first for the existence of the object with a test such as the following:

  if (Session["PowerUser"] == null)
      // No such value in session state; take appropriate action.

  2) Get Session value like the following:

  string powerUser= (string)(Session["PowerUser"]);

  3) Use the ChangeMode method to programmatically switch the DetailsView control between edit, insert, and read-only mode. This method also updates the CurrentMode property with the specified mode. The following table lists the different mode values.

  DetailsView.ChangeMode Method

  Let me know if your feedback.

  
  
  

  Thanks,
  Habib
• • Reply
  

  oned_gk

  All-Star

  35714 Points

  7294 Posts

  Re: System.NullReferenceException: Object reference not set to an instance of an object. - Trying...

  Nov 10, 2012 12:26 AM|LINK

  if (Session["PowerUser"] != null)
  {
         if (Session["PowerUser"] == "Y")
         {
             btnEdit.Visible = false;
         }
         else
         {
             btnEdit.Visible = true;
         }
  }

  Programming to simplify, dont look for hard way
  Suwandi - Non Graduate Programmer
  • Marked as answer by bbcompent1 on Nov 15, 2012 05:03 PM