Question

I’m wondering how to return the result from a SELECT COUNT statement in C#.

I have a sql statement that returns the count of 15.

Currently, I’m returning the datareader. Can I somehow return the result of that as a string?

    static public SqlDataReader FillDataReader(string sql, SqlParameter[] parms)
{
    SqlConnection conn = new SqlConnection(ConnectionString);
    SqlCommand cmd = new SqlCommand(sql, conn);
    SqlDataReader dr = null;
    conn.Open();
    cmd.CommandTimeout = 120; //120 seconds for the query to finish executing

    foreach (SqlParameter p in parms)
    {
        cmd.Parameters.Add(p);
    }
    try
    {
        dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
    }
    catch (SqlException ex)
    {
        if (dr != null)
        {
            dr.Close();
        }
        conn.Close();


        //DBUtilExceptionHandler(ex, sql);

        throw ex;


    }
    finally
    {
    }

    return dr; //This could be null...be sure to test for that when you use it

}

Or I could use a different method. I just don’t know what it should be.

Any help is appreciated.

This is my select statement:

        select count(LeadListID) from LeadLists WHERE SalesPersonID = 1
AND LeadListDateCreated BETWEEN '9/1/11' AND '10/1/11 23:59:59'

Answer 1

Sure – just use:

int count = (int) query.ExecuteScalar();
// TODO: Decide the right culture to use etc
return count.ToString();

Notes:

• Use using statements instead of manual try/catch/finally blocks
• You should close the connection whether or not there was an error
• Given that the natural result of the query is an integer, I would change it to return an int, not a string. Let the caller make that conversion if they want to
• If there’s an error, you should almost certainly let the exception bubble up, rather than returning null

I would write the code as:

public static int ExecuteScalarInt32(string sql, SqlParameter[] parms)
{
    using (SqlConnection conn = new SqlConnection(ConnectionString))
    using (SqlCommand command = new SqlCommand(sql, conn) { Parameters = parms })
    {
        conn.Open();
        command.CommandTimeout = 120;
        return (int) command.ExecuteScalar();
    }
}

If you really needed a version to work on an arbitrary data reader, you could write it as:

public static T ExecuteQuery<T>(string sql, SqlParameter[] parms,
                                Func<SqlDataReader, T> projection)
{
    using (SqlConnection conn = new SqlConnection(ConnectionString))
    using (SqlCommand command = new SqlCommand(sql, conn) { Parameters = parms })
    {
        conn.Open();
        command.CommandTimeout = 120;
        return projection(command.ExecuteReader());
    }
}

And then call it with:

int count = ExecuteQuery<int>(sql, parms, reader => {
                                  if (!reader.MoveNext()) {
                                      throw new SomeGoodExceptionType("No data");
                                  }
                                  return reader.GetInt32(0);
                              });