Parameterized Query Returns One Row With Null Values.

I am hoping someone could help me understand why this is happening and perhaps a solution.

I am using ASP.NET 2.0 with a SQL 2005 database.

In code behind, I am performing a query using a parameter as below:

sql = "SELECT field_name FROM myTable WHERE (field_name = @P1)"

objCommand.Parameters.Add(New SqlParameter("@P1", TextBox1.Text))

The parameter is obtained from TextBox1 which has valid input. However, the value is not in the table. The query should not return ANY results. However, I am getting one single row back with null values for each field requested in the query.

The SQL user account for this query has select, insert, and update permissions on the table. The query is simple, no joins, and the table has no null values in any fields. If I perform the exact same query using an account with select only permission on the table, I get what I was expecting, no records. Then if I go back to the previous user account with more permissioins, and I change the query to pass the paramter this way:

sql = String.Format("SELECT field_name FROM myTable WHERE (field_name = {0})", TextBox1.Text)

I also get NO records retuned using the same criteria.

What is going on here? I would prefer to use the parameterized query method with the account having elevated permissions. Is there some command object setting that can prevent the null row from returning?

Thanks!