What it wrong with this function ?

Question

private   void  btnAdd_Click( object  sender, EventArgs e)        {            {                con.Open();                 //string Sql = "INSERT INTO Members ( MemberId, Name, Address, Mobile, Email ) VALUES " + " (@Id, @name, @address, @mobile, @email)";                     string  Sql =  "INSERT INTO Members ( MemberId, Name, Address, Mobile, Email ) VALUES "  +  " (@Id, @name, @address, @mobile, @email); SELECT MemberId FROM Members WHERE NOT EXISTS (SELECT * FROM Members WHERE MemberId = @Id AND Name = @name AND Address = @address AND Mobile = @mobile AND Email = @email)" ;                    using  (SqlCommand cmd =  new  SqlCommand(Sql, con))                {                    cmd.CommandText = Sql;                    cmd.Parameters.AddWithValue( "@Id" , tbID.Text);                    cmd.Parameters.AddWithValue( "@name" , tbName.Text);                    cmd.Parameters.AddWithValue( "@address" , tbAddress.Text);                    cmd.Parameters.AddWithValue( "@mobile" , tbMobile.Text);                    cmd.Parameters.AddWithValue( "@email" , tbEmail.Text);                    cmd.ExecuteNonQuery();                        //Sql = "INSERT INTO Payments ( MemberId, [Year], [Amount] ) VALUES " + "(@id, @year, @amount)";                     Sql =  "INSERT INTO Payments ( MemberId, [Year], [Amount] ) VALUES "  +  "(@id, @year, @amount) SELECT MemberId FROM Payments WHERE NOT EXISTS (SELECT * FROM Payments WHERE [Year] = @year AND [Amount] = @amount)" ;                    cmd.Parameters.Clear();                    cmd.CommandText = Sql;                    cmd.Parameters.AddWithValue( "@Id" , tbID.Text);                    cmd.Parameters.AddWithValue( "@year" , tbYear.Text);                    cmd.Parameters.AddWithValue( "@amount" , tbAmount.Text);                    cmd.ExecuteNonQuery();                       MessageBox.Show( "Data Added" );                    tbID.Clear(); tbName.Clear(); tbAddress.Clear(); tbMobile.Clear(); tbEmail.Clear(); tbYear.Clear(); tbAmount.Clear();                    con.Close();                }            }        }   I have 2 tables "Members" & "Payments" When I enter one new record it records its and then if I enter the same over and over again it duplicates it many times which it "SHOULD NOT" I should get warning that it already exists. some how I am stuck with this can anyone assist !

Pankaj Kumar Choudhary · Accepted Answer

Hello! Jahangir to resolve this error either you can create the index on MemberId field or on other required fields. in such way a duplicate record will not insert. OR You can create a stored procedure in this stored procedure before inserting any record you can check the existence of record if record already exist then send a error message else insert the record into table...... In your case if duplicate data is inserting that means there is not a clustered or non clustered index in table so you can create a index on required field...........