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POHow to multibind data and StringFormat in a datagrid column?
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  1. POHow to multibind data and StringFormat in a datagrid column?
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    copied!<p>I have a WPF <code>DataGrid</code> with numeric columns that are initially formatted without decimals.</p> <p>The user has a checkbox to select the numeric format to show 0 or 2 decimal places. Below is shown the xaml for the column. </p> <pre><code>&lt;DataGridTemplateColumn Header="Qty" Width="40" IsReadOnly="False" CellStyle="{StaticResource EditCell}"&gt; &lt;DataGridTemplateColumn.CellTemplate&gt; &lt;DataTemplate&gt; &lt;TextBlock Text="{Binding ItemQuantity, StringFormat={}{0:#}}" TextAlignment="Right" /&gt; &lt;/DataTemplate&gt; &lt;/DataGridTemplateColumn.CellTemplate&gt; &lt;DataGridTemplateColumn.CellEditingTemplate&gt; &lt;DataTemplate&gt; &lt;TextBox x:Name="textbox" BorderThickness="0" HorizontalContentAlignment="Right" Background="LightYellow"&gt; &lt;Binding Path="ItemQuantity" StringFormat="N0" UpdateSourceTrigger="LostFocus" &gt; &lt;Binding.ValidationRules&gt; &lt;c:DecimalRangeRule Min="0" Max="999999.99"/&gt; &lt;/Binding.ValidationRules&gt; &lt;/Binding&gt; &lt;/TextBox&gt; &lt;/DataTemplate&gt; &lt;/DataGridTemplateColumn.CellEditingTemplate&gt; &lt;/DataGridTemplateColumn&gt; </code></pre> <p>How can I change the column <code>StringFormat</code> setting when the checkbox is changed?</p> <p><strong>EDIT: Solution</strong></p> <p>I used a MultiConverter (as suggested by nit) to select the format based on whether the checkbox is checked:</p> <pre><code>//========================================================================== public class NumericFormatConverter : IMultiValueConverter { private const string FormatN0 = "{0:#,##0;-#,##0; }"; private const string FormatN2 = "{0:#,##0.00;-#,##0.00; }"; public object Convert( object[] values, Type targetType, object parameter, CultureInfo culture ) { if ( values[0] == null ) return string.Empty; decimal num = 0; Decimal.TryParse( values[0].ToString(), out num ); string format = FormatN0; bool isSmallValue = (values[1] == null ? false : (bool)values[1]); if ( isSmallValue ) format = FormatN2; return String.Format( format, num ); } public object[] ConvertBack( object value, Type[] targetTypes, object parameter, CultureInfo culture ) { decimal num = 0; Decimal.TryParse( value.ToString(), out num ); object[] objects = new object[1] {num}; return objects; } } </code></pre> <p>The DataGridTemplateColumn changed to use MultiBinding:</p> <pre><code>&lt;DataGridTemplateColumn Header="Qty" Width="40" IsReadOnly="False" CellStyle="{StaticResource EditCell}"&gt; &lt;DataGridTemplateColumn.CellTemplate&gt; &lt;DataTemplate&gt; &lt;TextBlock HorizontalAlignment="Right" &gt; &lt;TextBlock.Text&gt; &lt;MultiBinding Converter="{StaticResource NumericFormat}"&gt; &lt;Binding Path="GroupQuantity" /&gt; &lt;Binding ElementName="chkSmallValue" Path="IsChecked"/&gt; &lt;/MultiBinding&gt; &lt;/TextBlock.Text&gt; &lt;/TextBlock&gt; &lt;/DataTemplate&gt; &lt;/DataGridTemplateColumn.CellTemplate&gt; &lt;DataGridTemplateColumn.CellEditingTemplate&gt; &lt;DataTemplate&gt; &lt;TextBox x:Name="textbox" BorderThickness="0" HorizontalContentAlignment="Right" Background="LemonChiffon" PreviewTextInput="TextBox_PreviewTextInput" &gt; &lt;MultiBinding Converter="{StaticResource NumericFormat}" UpdateSourceTrigger="LostFocus"&gt; &lt;Binding Path="GroupQuantity" /&gt; &lt;Binding ElementName="chkSmallValue" Path="IsChecked" Mode="OneWay"/&gt; &lt;/MultiBinding&gt; &lt;/TextBox&gt; &lt;/DataTemplate&gt; &lt;/DataGridTemplateColumn.CellEditingTemplate&gt; &lt;/DataGridTemplateColumn&gt; </code></pre>
 

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