救救我吧，实在搞不定，这方法哪错了？

C# code

   var tb = SQLHelper.GetTable("select * from bjx_zt");

C# code

    /// <summary>    /// 返回指定Sql语句的DataTable    /// </summary>    /// <param name="strSql">传入的Sql语句</param>    /// <returns>DataTable</returns>    public static DataTable GetTable(string strSql)    {        SqlDataAdapter da = new SqlDataAdapter();        DataTable datatable = new DataTable();        try        {            using (SqlConnection connection = new SqlConnection(StrConn))            {                using (SqlCommand cmd = new SqlCommand(strSql, connection))                {                    try                    {                        connection.Open();                        cmd.CommandType = CommandType.Text;                        da.SelectCommand = cmd;                        da.Fill(datatable);                    }                    catch                    {                        connection.Close();                    }                }            }        }        catch { }        return datatable;    }

这怎么老返回空呢，
我表里有内容， 数据库链接也没错，求救大牛....

[解决办法]
SqlConnection conn = new SqlConnection(sqlConnectionString);

conn.Open();

SqlCommand cmd = new SqlCommand();

cmd.Connection = conn;

cmd.CommandType = CommandType.Text;

cmd.CommandText = commandText;

SqlDataAdapter da = new SqlDataAdapter(cmd);

DataSet ds = new DataSet();

try

{

da.Fill(ds);

}

[解决办法]

C# code

    /// <summary>    /// 返回指定Sql语句的DataTable    /// </summary>    /// <param name="strSql">传入的Sql语句</param>    /// <returns>DataTable</returns>    public static DataTable GetTable(string strSql)    {        DataTable datatable = new DataTable();        try        {            using (SqlConnection connection = new SqlConnection(StrConn))            {                  SqlDataAdapter adapter = new SqlDataAdapter(strSql,connection);                  DataSet ds = new DataSet();                  adapter.Fill(ds);                  datatable  = ds.Tables[0];            }        }        catch { }        return ds;    }
[解决办法]
   /// <summary>
   /// 返回指定Sql语句的DataTable
   /// </summary>
   /// <param name="strSql">传入的Sql语句</param>
   /// <returns>DataTable</returns>
   public static DataTable GetTable(string strSql)
   {
       DataTable datatable = new DataTable();
       try
       {
           using (SqlDataAdapter adapter = new SqlDataAdapter(strSql,StrConn))
           {                 
                 DataSet ds = new DataSet();
                 adapter.Fill(ds);
                 datatable  = ds.Tables[0];
           }
       }
       catch { }
       return ds;
   }