Question

I want to use a select statement to find if there is a record that already exists. I’ve put the code below but it throws an error at the dReader = comm.ExecuteReader(); and i’m unsure why. Any help?

    string connString = "Data Source=KIMMY-MSI\\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True";

    SqlDataReader dReader;
    SqlConnection conn = new SqlConnection(connString);
    SqlCommand comm = new SqlCommand();
    comm.Connection = conn;

    comm.CommandText = "SELECT * FROM Customers WHERE CustomerID == " + txtID.Text;
    comm.Connection.Open();

    dReader = comm.ExecuteReader();

    if (dReader.HasRows == true)
    {
        Response.Write("Exists");
    }

The error:

Invalid Column Name (whatever I input)

It seems to be looking for a column named what I input rather than looking for the actual data.

Answer 1

Change your == to =. That is invalid SQL as it is.

Also if txtID.Text is non-numeric then it needs to be in single quotes. You should not be constructing your SQL like this, instead use a parameter:

comm.CommandText = "SELECT * FROM Customers WHERE CustomerID = @CustomerID";
comm.Parameters.AddWithValue("CustomerID", txtID.Text);    

More Info

C# using statement

SQL reference

SQL injection (why you should parameterize your queries)