how to send parameters to a query

When you use Sql Server 2000 you specify parameter names in the query or if you use the ? then when you add parameters to the sqlcommand it will replace the ? in the order in which they appear.

Example: Assumes Nortwind Database and that sqlConnection1 has already been initialized

sqlConnection1.Open();
SqlCommand cmd = new SqlCommand("select * from Categories where CategoryID=@CatId",sqlConnection1);

// Create a new parameter with the name of the parameter and in this case the value
SqlParameter par = new SqlParameter("@CatId",2);

cmd.Parameters.Add(par);

SqlDataReader dr = cmd.ExecuteReader();

while(dr.Read())
{
       MessageBox.Show(dr[0].ToString());
}
sqlConnection1.Close();