/// <summary>
/// no caching
/// </summary>
/// <param name="tableName"></param>
/// <param name="type"></param>
/// <param name="columns"></param>
/// <param name="sql"></param>
/// <returns></returns>
public static DataTable GetTable(string tableName, AppVar.ConnectionStringType type, string[] columns = null,
string sql = null)
{
var connectionString = AppVar.GetConnectionString(type);
return(GetTable(tableName, connectionString, columns, sql));
}