Problem in Null object

Greeting

I used gridview in my system to review users, anyway when I need to delete user, I need to deleted all rows in many tables depends on UserId. Actually I created a stored procedure take an input parameter (UserId) from gridview.

See gridview code herer

"gvbremployee" runat="server" AllowSorting="True" AutoGenerateColumns="False" Font-Size="Medium" Width="60%" DataKeyNames="UserId" DataSourceID="SDS_BR_DLL" EmptyDataText="Sorry! No staff in selected branch." OnSelectedIndexChanged="gvbremployee_SelectedIndexChanged" OnRowDeleting="gvbremployee_RowDeleting">
"False">
"LnkBtn_Sel" runat="server" CausesValidation="False" CommandName="Select" class="btn btn-outline-primary">class="fa fa-folder-open">
"LnkBtn_del" runat="server" CausesValidation="False" CommandName="Delete" OnClientClick="return confirm('Are you sure you want to delete Employee row?')" class="btn btn-outline-danger">class="fa fa-trash" aria-hidden="true">
"UserId" Visible="False" HeaderText="UserId" />
"UserName" HeaderText="UserName"/>
"S_Gender" HeaderText="Gender" SortExpression="S_Gender" />
"S_Salary" HeaderText="Salary" SortExpression="S_Salary" />
"S_Status" HeaderText="Status" SortExpression="S_Status" />

Code behide for delete user event in gridview

protected void gvbremployee_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
try
{
GridViewRow row = (GridViewRow)gvbremployee.Rows[e.RowIndex];
string idvalue = gvbremployee.DataKeys[row.RowIndex].Values["UserId"].ToString();
using (SqlConnection sqlcon = new SqlConnection(Constr))
{
SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["Constr"].ConnectionString);
SqlCommand comm = new SqlCommand();
comm.CommandText = "del_user"; //this stored procedure and has an ID called UserId
comm.CommandType = CommandType.StoredProcedure;
//Pass the value here
comm.Parameters.AddWithValue("@UserId", idvalue);
comm.Connection = conn;
conn.Open();
comm.ExecuteNonQuery();
conn.Close();
}
}
catch (Exception ex)
{
Lbinfo.Text = ex.Message;
Lbinfo.ForeColor = System.Drawing.Color.Red;
}
}

Stored Procedure code

CREATE PROCEDURE [dbo].[del_user]
AS
DECLARE @UserId uniqueidentifier
SET @UserId = 'THE GUID OF THE USER HERE'
DELETE FROM Profiles WHERE UserId = @UserId
DELETE FROM UsersInRoles WHERE UserId = @UserId
DELETE FROM Memberships WHERE UserId = @UserId
DELETE FROM Users WHERE UserId = @UserId
DELETE FROM Staff WHERE UserId = @UserId
RETURN 0

When I execute app. and delete user an error messge is:

Object reference not set to an instance of an object.

That's mean a null in send parameter to stored procedure

A first chance exception of type 'System.NullReferenceException' occurred in WebApplication1.dll , can not able to catch (UserId) Valye

I change method

string idvalue = gvbremployee.DataKeys[row.RowIndex].Values["UserId"].ToString();

object idvalue = gvbremployee.Rows[e.RowIndex].Cells[0].UniqueID;

So what a problem, please.

Many thanks

protected void gvbremployee_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
try
{
GridView gvbremployee= (GridView)sender;
int row = e.RowIndex;
string idvalue = gvbremployee.DataKeys[row].Values[0].ToString();
using (SqlConnection sqlcon = new SqlConnection(Constr))
{
SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["Constr"].ConnectionString);
SqlCommand comm = new SqlCommand();
comm.CommandText = "del_user"; //this stored procedure and has an ID called UserId
comm.CommandType = CommandType.StoredProcedure;
//Pass the value here
comm.Parameters.AddWithValue("@UserId", idvalue);
comm.Connection = conn;
conn.Open();
comm.ExecuteNonQuery();
conn.Close();
}
}
catch (Exception ex)
{
Lbinfo.Text = ex.Message;
Lbinfo.ForeColor = System.Drawing.Color.Red;
}
}

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Aktham Mahmoud5y ago
Hi

Jignesh Kumar

I explained lastly in my whole description above

UserId : uniqueidentifier
Jignesh Kumar5y ago
1. protected void gvbremployee_RowDeleting(object sender, GridViewDeleteEventArgs e)
2. {
4. try
5. {
6. GridView gvbremployee= (GridView)sender;
  int row = e.RowIndex;
7. string idvalue = gvbremployee.DataKeys[row].Values[0].ToString();
9. using (SqlConnection sqlcon = new SqlConnection(Constr))
10. {
12. SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["Constr"].ConnectionString);
14. SqlCommand comm = new SqlCommand();
15. comm.CommandText = "del_user"; //this stored procedure and has an ID called UserId
16. comm.CommandType = CommandType.StoredProcedure;
17. //Pass the value here
18. comm.Parameters.AddWithValue("@UserId", idvalue);
19. comm.Connection = conn;
21. conn.Open();
22. comm.ExecuteNonQuery();
23. conn.Close();
24. }
25. }
26. catch (Exception ex)
27. {
28. Lbinfo.Text = ex.Message;
29. Lbinfo.ForeColor = System.Drawing.Color.Red;
31. }
33. }
For store procedure you need to pass parameter and same parameter need to use in where clause of delete statement .

You need to change your store procedure as below,
1. Alter PROCEDURE [dbo].[del_user]
2. @UserId varchar(100)
3. AS
4. Begin
5. DELETE FROM Profiles WHERE UserId = @UserId
6. DELETE FROM UsersInRoles WHERE UserId = @UserId
7. DELETE FROM Memberships WHERE UserId = @UserId
8. DELETE FROM Users WHERE UserId = @UserId
9. DELETE FROM Staff WHERE UserId = @UserId
10. End
for reference you can use this link,
https://forums.asp.net/t/1671239.aspx?Delete+records+in+Gridview+with+multi+datakeynames+in+GridView+