How can I say "Code not found"?

Question

Hi! How can I receive a message saying for example: " Code not found. Thanx ! " See what I wrote and its doenst result: private void btnSearch_Click(object sender, EventArgs e) { string connectionString = @"Data Source=localhost\sqlexpress;Initial Catalog=master;Integrated Security=True"; SqlConnection sqlCon = new SqlConnection(connectionString); sqlCon.Open(); string commandString = "select code, product, stocks from searching where code='" + code.Text + "'"; SqlCommand sqlCmd = new SqlCommand(commandString, sqlCon); SqlDataReader read = sqlCmd.ExecuteReader(); while (read.Read()) { code.Text = read["code"].ToString(); product.Text = read["product"].ToString(); Stocks.Text = read["stocks"].ToString(); } //problem start here else { MessageBox.Show("Code not found. Thanx!"); } } catch (Exception ex) { MessageBox.Show(ex.Message); } sqlCon.Close(); }

Vulpes · Answer

If you've uncommented the red line, then I can't see what else can possibly be null here so you you'll need to try and indentify the offending line with the debugger. Just one point though. Is the 'code' column a numeric or char based column in the database? If it's numeric, then you won't need the surrounding single quotes in the SELECT query.

Israel · Answer

Its running very well. Don't worry. But in runinng time when I put a code in the code textbox (code.Text). Then when I click its showing that message. Running its do it well. Just after click... The message appear.

Vulpes · Answer

First of all, if you uncomment the red line, does the code build OK? If it does, are you getting a null reference exception when you try to run it and are you able to pinpoint, using the debugger, on which line the exception occurs?

Israel · Answer

please let see what I do. I have this message: Object reference not set to an instance of an object private void btnSearch_Click(object sender, EventArgs e) { SqlConnection sqlCon = null; SqlDataReader read= null; try { string connectionString = @"Data Source=localhost\sqlexpress;Initial Catalog=master;Integrated Security=True"; //sqlCon = new SqlConnection(connectionString); sqlCon.Open(); string commandString = "select code, product, stocks from searching where code='" + code.Text + "'"; SqlCommand sqlCmd = new SqlCommand(commandString, sqlCon); read = sqlCmd.ExecuteReader(); while (read.Read()) { code.Text = read["code"].ToString(); product.Text = read["product"].ToString(); Stocks.Text = read["stocks"].ToString(); } } catch(IndexOutOfRangeException) { MessageBox.Show("Code not found. Thanx!"); } catch(Exception ex) { MessageBox.Show(ex.Message); } finally { read.Close(); sqlCon.Close(); } }

Vulpes · Answer

Notice that I've placed the declarations for the variables sqlCon and read at the top of the method. They shouldn't be declared again within the try statement or you'll get the compiler error you're now getting - they should simply be assigned to.

Israel · Answer

A local variable named 'sqlCon' cannot be declared in this scope because it would give a different meaning to 'sqlCon', which is already used in a 'parent or current' scope to denote something else A local variable named 'read' cannot be declared in this scope because it would give a different meaning to 'read', which is already used in a 'parent or current' scope to denote something else

Vulpes · Answer

If you're sure that "Code" is the only column which might not be found, you could do this: private void btnSearch_Click(object sender, EventArgs e) { SqlConnection sqlCon = null; SqlDataReader read= null; try { string connectionString = @"Data Source=localhost\sqlexpress;Initial Catalog=master;Integrated Security=True"; sqlCon = new SqlConnection(connectionString); sqlCon.Open(); string commandString = "select code, product, stocks from searching where code='" + code.Text + "'"; SqlCommand sqlCmd = new SqlCommand(commandString, sqlCon); read = sqlCmd.ExecuteReader(); while (read.Read()) { code.Text = read["code"].ToString(); product.Text = read["product"].ToString(); Stocks.Text = read["stocks"].ToString(); } } catch(IndexOutOfRangeException) { MessageBox.Show("Code not found. Thanx!"); } catch(Exception ex) { MessageBox.Show(ex.Message); } finally { read.Close(); sqlCon.Close(); } }

How can I say "Code not found"?

Francis