public static Task BuildupAsync( this IDataGridColumnBuilder builder, ICollection<DataGridColumn> columns, ColumnBuildOrders buildOrders )
 {
     Arg.NotNull( builder, nameof( builder ) );
     Arg.NotNull( columns, nameof( columns ) );
     Contract.Ensures( Contract.Result<Task>() != null );
     return builder.BuildupAsync( columns, buildOrders, CancellationToken.None );
 }
 Task IDataGridColumnBuilder.AppendToAsync( ICollection<DataGridColumn> columns, ColumnBuildOrders buildOrders, CancellationToken cancellationToken )
 {
     Contract.Requires<ArgumentNullException>( columns != null, "columns" );
     Contract.Requires<InvalidOperationException>( !columns.IsReadOnly, "columns" );
     Contract.Requires<ArgumentOutOfRangeException>( buildOrders != ColumnBuildOrders.None, "buildOrders" );
     Contract.Ensures( Contract.Result<Task>() != null );
     return null;
 }