---
lang: ja-jp
breaks: true
---
# `WinUI 3` `DataGridColumn` の表示内容をフォーマットする 2022-08-21


## IValueConverter

public sealed class SizeConverter :
    Microsoft.UI.Xaml.Data.IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string language)
    {
        if (value == null)
        {
            return null;
        }

        if (value is int)
        {
            return GetIntStringWithComma(value as int?);
        }

        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, string language)
    {
        if (value == null)
        {
            return null;
        }
        return value;
    }

    public static string GetIntStringWithComma(int? val)
    {
        if (!val.HasValue)
        {
            return "";
        }

        if (val.Value >= 0)
        {
            return val.Value.ToString("#,0");
        }

        return $"-{(val.Value * -1).ToString("#,0")}";
    }
}

:::warning
`IValueConverter`は、`System.Windows.Data.IValueConverter`ではない、**`Microsoft.UI.Xaml.Data.IValueConverter`**。
:::

## MainWindow.xaml

・・・
<controls:DataGrid 
    ItemsSource="{x:Bind ViewModel.PackagesList, Mode=OneWay}"
    >
    <controls:DataGrid.Resources>
        <helpers:SizeConverter x:Key="SizeConverter" />
    </controls:DataGrid.Resources>
    
    <controls:DataGrid.Columns>
        <controls:DataGridTextColumn 
            Header="Size" 
            Binding="{Binding Path=Size, Converter={StaticResource SizeConverter}}" 
            Tag="Size" 
            x:Name="DataGridColumn_Size"
            >
        </controls:DataGridTextColumn>
    </controls:DataGrid.Columns>
</controls:DataGrid>
・・・

###### tags: `WinUI 3` `DataGridColumn` `IValueConverter` `フォーマット` `format`