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wpf - 通过转换器从DataGrid中的2计算一列

问题描述

我正在编写显示数据网格中产品数据的应用程序（我第一次使用 WPF）。我成功地将数据网格与 MS SQL 数据库连接起来。我坚持创建计算列。我有兴趣将两列的值相乘。我想使用Pcs_DC_col和Qty_multi_col来计算 Qty_DC_col 中的值。据我了解，我必须使用转换器，因为我使用超过 1 个列，我应该使用 IMultiValueConverter。但是不知道如何编写代码来向我展示与空白单元格或dependencyproperty.unsetvalue不同的东西。我应该添加或更改什么才能使其正常工作？

XAML 代码： 

<Window.Resources>
        <local:ColumnConverter x:Key="ColumnConversion"/>
    </Window.Resources>
    
    <Grid>
                    <DataGrid x:Name="matrix" SelectionUnit="FullRow" SelectionChanged="PLU_row_selected" 
                              AutoGenerateColumns="False" CanUserAddRows="False">
                      
                        <DataGrid.Columns>
                            <DataGridTextColumn Header="PLU" Binding="{Binding PLU}"/>
                            <DataGridTextColumn Header="config" Binding="{Binding config}"/>
                            <DataGridTextColumn Header="Name" Binding="{Binding Name}"/>
                            <DataGridTextColumn Header="Colour" Binding="{Binding Colour}"/>
                            <DataGridTextColumn Header="Promo" Binding="{Binding Promo}"/>
                            <DataGridTextColumn Header="Department" Binding="{Binding Department}"/>
                            <DataGridTextColumn Header="Category" Binding="{Binding Category}"/>
                            <DataGridTextColumn Header="Price" Binding="{Binding Price}"/>
                            <DataGridTextColumn x:Name="Pcs_DC_col" Header="Pc.s DC" Binding="{Binding Pcs Dc}"/>
                            <DataGridTextColumn Header="Allocated Pcs" Binding="{Binding Allocated Pcs}"/>

                            <DataGridTextColumn x:Name="Qty_DC_col" Header="Qty DC">
                                <DataGridTextColumn.Binding>
                                    <MultiBinding Converter="{StaticResource ColumnConversion}">
                                        <Binding ElementName="Pcs_DC_col" Path="Text"/>
                                        <Binding ElementName="Qty_multi_col" Path="Text"/>
                                    </MultiBinding>
                                </DataGridTextColumn.Binding>
                            </DataGridTextColumn>                            
                          
                            <DataGridTextColumn Header="Qty All" Binding="{Binding obliczenia}"/>
                            <DataGridTextColumn Header="Qty Tra" Binding="{Binding  Qty Tra}"/>
                            <DataGridTextColumn Header="Qty Str" Binding="{Binding  Qty Str}"/>
                            <DataGridTextColumn x:Name="Qty_multi_col" Header="Qty multiple" Binding="{Binding Qty Multiple}"/>
                            <DataGridTextColumn Header="% all" Binding="{Binding Percent_Allo}"/>
                            <DataGridTextColumn Header="Value all" Binding="{Binding Value_allocated}"/>
                        </DataGrid.Columns>
                    </DataGrid>
    </Grid>

转换器代码：

public class ColumnConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if (values == null) return 0;

        try
        {
            return String.Format("{0}", values[0]);
        } 

        catch
        {
            return 0;
        }

    } // Convert()

此版本向我显示空白列，如果我更改以下代码：

 return String.Format("{0}", values[0]);

用dependencyproperty.unsetvalue填充我的专栏。

编写如何将数据从数据库加载到网格的代码：

  private void load_products_to_grid()
    {
        SqlConnection myConnection = new SqlConnection();
        myConnection.ConnectionString = @"Server = batorego426\coreSQL; Database = CorpCore; Integrated Security=true;";
        myConnection.Open();
        SqlCommand query = new SqlCommand();
        query.CommandText = "select * from [products]";
        query.Connection = myConnection;
        SqlDataAdapter adapter = new SqlDataAdapter(query);
        DataTable product_table = new DataTable("products");
        adapter.Fill(product_table);

        matrix.ItemsSource = product_table.DefaultView;
    }

编辑：

我按照安迪的建议改变了竞价

<DataGridTextColumn x:Name="Qty_DC_col" Header="Qty DC">
                            <DataGridTextColumn.Binding>
                                <MultiBinding Converter="{StaticResource ColumnConversion}">
                                    <Binding Path="Pcs_DC_col"/>
                                    <Binding Path="Qty_multi_col"/>
                                </MultiBinding>
                            </DataGridTextColumn.Binding>
                        </DataGridTextColumn>

和转换器代码：

 public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if (values == null) return 0;

            return (int)values[0]*(int)values[1];
    }

但我仍然得到空列，我尝试在转换器中更改代码以检查是否可以看到任何值：

String.Format("{0}", values[0]);

但是然后在该列中获取“dependencyproperty.unsetvalue” 。所以我猜数据仍然没有连接，甚至不是空的，但没有 tset。我还能做什么？

标签： wpfdata-bindingdatagridcalculated-columns

解决方案

您在多重绑定中的绑定应该是数据和列名。如果它们是 Pcs_DC_col 和 Qty_multi_col 那么

<MultiBinding Converter="{StaticResource ColumnConversion}">
      <Binding  Path="Pcs_DC_col"/>
      <Binding  Path="Qty_multi_col"/>
</MultiBinding>

object[] values 数组中有两个值。这些可能是双倍的，但据代码所知，这些只是对象，因此将它们强制转换并将它们加在一起。将其作为数字返回。就像是：

return (double)values[0] * (double)values[1];

You may have to null trap etc. And that column better not be editable.

For most datagrids I would have a viewmodel to represent each row out the database and I could put calculations etc in there. So there'd be a property which summed the two columns. And of course I'd have somewhere to put other logic such as validation. Binding directly to a datatable is quite limiting.

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