get last inserted primary key record in database - vb.net

Question

Please help to get the primary key of the last insert record as the one which i have gives me duplicate rows in the database and return 0
Try
If Conn.State = ConnectionState.Open Then Conn.Close()
'insert the new customer data
Conn.Open()
cmd = New SqlCommand("insert into Quote values ('" & dateOFCreat & "','" & Emp & "','" & Customer_no & "' )", Conn)
Dim a As Integer = cmd.ExecuteNonQuery()
Dim results As Integer
Dim cmd_results As SqlCommand
'Get the last created Quote in the Database
cmd_results = New SqlCommand("Select ##Identity from Quote", Conn)
results = cmd.ExecuteScalar
TxtLastQuoteID.Text = results
If a = 0 Then
MsgBox("Error")
End If
Conn.Close()
Catch ex As Exception
MsgBox(ex.Message)
End Try

Answer 1

You can make use of the batch commands supported by Sql Server. Just put together the two instructions and just use ExecuteScalar. However, before that, you need to fix ASAP your Sql Injection vulnerability. Do not concatenate strings to build an sql command, but use parameters.
Try
Using con as SqlConnection = new SqlConnection(....constringhere...)
Conn.Open()
Dim sqlText = "insert into Quote values (#dat,#emp,#cusno); SELECT SCOPE_IDENTITY()"
cmd = New SqlCommand(sqlText,Conn)
cmd.Parameters.Add("#dat", SqlDbType.NVarChar).Value = dateOFCreat
cmd.Parameters.Add("#end", SqlDbType.NVarChar).Value = emp
cmd.Parameters.Add("#cusno", SqlDbType.NVarChar).Value = Customer_no
Dim lastID As Integer = cmd.ExecuteScalar()
TxtLastQuoteID.Text = lastID.ToString()
Conn.Close()
End Using
Catch ex As Exception
MsgBox(ex.Message)
End Try
Notice also that is a very bad thing to keep a global connection object. You don't need that because ADO.NET implements Connection Pooling that makes opening a connection a very fast operation. Instead keeping a connection around requires a lot of effort to work correctly around it
Finally you can look here to better understand the difference between SCOPE_IDENTITY and ##IDENTITY and why is usually better to use the first one.