Scalar variable must be declared.

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I want to delete a row from datagrid and datatable. So I wrote the following process to be done.
Now my error is that the Scalar variable is not declared. I literally don't know how to fix this

What I have tried:

C#

int selectedIndex = datagriduser.SelectedIndex;
               DataRowView rowview = datagriduser.SelectedItem as DataRowView;
               //  string cltyp = rowview["ClientTyp"].ToString();
               var cltyp = "";
               var macadress = "";
               var userkenn = "";
                // OleDbCommand olecmd = new OleDbCommand("DELETE From AktiveUser WHERE User_Kennzeichen = 'nh'", conn);
               string query = "DELETE From AktiveUser WHERE ClientTyp= @cltyp AND MAC_Adresse =  @macadress AND User_Kennzeichen = @userkenn";
               OleDbCommand olecmd = new OleDbCommand(query, conn);
              // olecmd.ExecuteNonQuery();
               // OleDbCommand olecmd = new OleDbCommand("DELETE From AktiveUser WHERE User_Kennzeichen = 'nh'", conn);
               olecmd.Parameters.AddWithValue(@cltyp, rowview["ClientTyp"].ToString());
               olecmd.Parameters.AddWithValue(@macadress, rowview["Arbeitsplatz"].ToString());
               olecmd.Parameters.AddWithValue(@userkenn, rowview["Anmeldung"].ToString());
               if (selectedIndex != -1)
               {
                   var deletedrow = dbtable.Rows[selectedIndex];
                   deletedrow.Delete();
                   oleda.DeleteCommand = olecmd;
                   oleda.Update(dbtable);
               }
               else
               {
                   System.Windows.MessageBox.Show("Please Select a row to Delete");
               }

Posted 20-Feb-19 2:13am

Priya Karthish

Updated 20-Feb-19 3:57am

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2 solutions

Solution 1

You haven't put quotes around @cltyp and the two others, so now it just refers to the value of the cltyp variable - which is an empty string. Put quotes around @cltyp, @macadress and @userkenn.

Posted 20-Feb-19 2:17am

Thomas Daniels

Comments

Priya Karthish 20-Feb-19 8:28am

singlequote rite

Priya Karthish 20-Feb-19 8:32am

I tried putting both singlequote and doublequote. It's not working still

Richard Deeming 20-Feb-19 9:53am

Not in the query - in the AddWithValue lines.

What you've got at the moment is effectively:

olecmd.Parameters.AddWithValue("", rowview["ClientTyp"].ToString());

It needs to be:

olecmd.Parameters.AddWithValue("@cltyp", rowview["ClientTyp"].ToString());

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MadMyche · Accepted Answer · 2019-02-20T03:57:00

You have two mistakes here; the first is that the parameters being added need to be within double quotes (as the prior answers have pointed out).

The other is that the OleDB database provider does not support named parameters within the query itself.
OleDbCommand.Parameters Property (System.Data.OleDb) | Microsoft Docs[^]

OleDB Documentation
The OLE DB .NET Provider does not support named parameters for passing parameters to an SQL statement or a stored procedure called by an OleDbCommand when CommandType is set to Text. In this case, the question mark (?) placeholder must be used.

Try these changes to your problem

C#

string query = "DELETE From AktiveUser WHERE ClientTyp= ? AND MAC_Adresse =  ? AND User_Kennzeichen = ?";
OleDbCommand olecmd = new OleDbCommand(query, conn);

olecmd.Parameters.AddWithValue("@cltyp", rowview["ClientTyp"].ToString());
olecmd.Parameters.AddWithValue("@macadress", rowview["Arbeitsplatz"].ToString());
olecmd.Parameters.AddWithValue("@userkenn", rowview["Anmeldung"].ToString());