ASP.net delete row using gridview

Question

I'm trying to delete a row using the delete function provided trouhg to gridview wizard.

But when i click on delete I get following error:

An exception of type 'System.InvalidOperationException' occurred in System.Data.Linq.dll but was not handled in user code

This is my code:

 public void deleteProject(DAL.Project p)
    {
        DAL.Project result = (from project in dc.Projects
                              where project.pk_project_id == p.pk_project_id
                              select project).Single();
        dc.Projects.DeleteOnSubmit(result);
        dc.SubmitChanges();
    }

when I debug it the value "p" has no properties.

The strange thing is that when I want to update my rows I use somewhat the same method:

 DAL.Project result = (from project in dc.Projects
                              where project.pk_project_id == p.pk_project_id
                              select project).Single();
        result.titel = p.titel;
        result.beschrijving = p.beschrijving;

        dc.SubmitChanges();

This goes well. So why doesn't it work with deleting rows?

it looks like DAL.Project is not being assigned before calling deleteProject, what is different about the update method? — Patrick Developer
– Patrick Developer, Commented Aug 27, 2014 at 13:04
Indeed when I call the delete method "p" = null, but when calling update it is not null. The strange this is i call them both in the same way so their shouldn't be a problem. — user683326
– user683326, Commented Aug 27, 2014 at 13:28
You will need to figure out what is different between the two methods and the code that executes these methods. — Patrick Developer
– Patrick Developer, Commented Aug 27, 2014 at 13:53

Tim Schmelter · Accepted Answer · 2014-08-27 13:05:06Z

1

Enumerable.Single throws an InvalidOperationException if the sequnce contains more than one item or theinput sequence is empty. You can use First or FirstOrDefault:

DAL.Project result = (from project in dc.Projects
                      where project.pk_project_id == p.pk_project_id
                      select project).FirstOrDefault();
if(result != null)
{
     // ...
}

(However, i don't know why the update work )

answered Aug 27, 2014 at 13:05

Tim Schmelter

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