FetchData.cs

private DataTable FetchData(string tableName)
{
    using (SqlConnection conn = new SqlConnection(_connectionString))
    {
        string sQuery = "SELECT * FROM [" + tableName + "]";
        using (SqlCommand command = new SqlCommand(sQuery, conn))
        {
            conn.Open();
            command.CommandTimeout = 180; 
            DataAdapter da = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            da.Fill(ds);
            DataTable dt = ds.Tables[0];
            dt.TableName = tableName;
            ds.Tables.Remove(dt);
            return dt;
        }
    }
}