作为学习在WPF中正确使用绑定的一部分，我创建了一个小型转换程序，将温度，长度，分数转换为小数等。在完成此操作后，温度和分数一切正常使用简单的绑定和转换器。我在长度转换方面遇到了问题，因为它需要MultiBinding才能起作用。
对于控件，我使用两个文本框表示原始长度和转换后的长度。每一个都有一个匹配的组合框，用户可以在其中选择度量单位（即厘米，英寸，毫米等）。
使用断点，我确定条目将进入Convert方法，并且该方法中的代码可以正确计算所有内容。 result变量甚至在方法调用结束时显示正确转换的数字，但是该数字并不能将其返回到lengthResult TextBox中。
我已经尝试了所有可以想到的迭代，以使其运行起来，并在Google上搜索了大约3个小时。我找不到问题，也没有找到足够类似的情况的指南，无法解决该问题。有人可以看看这个并找到我正在犯的（很有可能）简单错误吗？
注意：我在C＃代码中有一个ConvertBack函数，但是除了默认的throw new NotImplementedException之外，它什么都没有，所以我省略了它。我会担心Convert首先工作之后。 ：）
XAML：
<GroupBox Header="Length" DockPanel.Dock="Top">
<GroupBox.Resources>
<local:LengthConverter x:Key="lengthConverter" />
</GroupBox.Resources>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Label Content="Original Length:" Grid.Column="0" Grid.Row="0" VerticalAlignment="Center" HorizontalAlignment="Right" Margin="10" />
<Label Content="Destination Length:" Grid.Column="0" Grid.Row="1" VerticalAlignment="Center" HorizontalAlignment="Right" Margin="10" />
<ComboBox x:Name="originUnitSelect" Grid.Column="2" Grid.Row="0" ItemsSource="{Binding Units}" Height="{Binding ElementName=lengthEntry, Path=ActualHeight}" MinWidth="50" />
<ComboBox x:Name="destinationUnitSelect" Grid.Column="2" Grid.Row="1" ItemsSource="{Binding Units}" Height="{Binding ElementName=lengthResult, Path=ActualHeight}" MinWidth="50" />
<TextBox x:Name="lengthEntry" Grid.Column="1" Grid.Row="0" VerticalAlignment="Center" Margin="10" HorizontalContentAlignment="Center" MinWidth="250" />
<TextBox x:Name="lengthResult" Grid.Column="1" Grid.Row="1" VerticalAlignment="Center" Margin="10" HorizontalContentAlignment="Center" MinWidth="250">
<TextBox.Text>
<MultiBinding Converter="{StaticResource lengthConverter}">
<Binding ElementName="lengthEntry" Path="Text" UpdateSourceTrigger="PropertyChanged" />
<Binding ElementName="originUnitSelect" Path="SelectedValue" />
<Binding ElementName="destinationUnitSelect" Path="SelectedValue" />
</MultiBinding>
</TextBox.Text>
</TextBox>
<Button x:Name="convertLength" Grid.Column="1" Grid.Row="2" Content="Convert" VerticalAlignment="Center" HorizontalAlignment="Center" Click="convertLength_Click" Margin="10"/>
</Grid>
</GroupBox>
C＃：
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
double result = 0.0;
double cm_to_mm = 10;
double cm_to_in = 0.3937;
double cm_to_ft = 0.32808;
double cm_to_yd = 0.010936;
double mm_to_cm = 0.10;
double mm_to_in = mm_to_cm * cm_to_in;
double mm_to_ft = mm_to_cm * cm_to_ft;
double mm_to_yd = mm_to_cm * cm_to_yd;
double in_to_mm = 25.4;
double in_to_cm = 2.54;
double in_to_ft = 1 / 12;
double in_to_yd = 1 / 36;
double ft_to_yd = 36;
double ft_to_in = 12;
double ft_to_cm = ft_to_in * in_to_cm;
double ft_to_mm = ft_to_in * in_to_mm;
double yd_to_ft = 3;
double yd_to_in = 36;
double yd_to_cm = ft_to_in * in_to_cm;
double yd_to_mm = ft_to_in * in_to_mm;
if(values[1] != null && values[2] != null)
{
switch(values[1].ToString())
{
case "mm":
if (double.TryParse(values[0].ToString(), out result))
{
switch(values[2].ToString())
{
case "cm":
result = result * mm_to_cm;
break;
case "in":
result = result * mm_to_in;
break;
case "ft":
result = result * mm_to_ft;
break;
case "yd":
result = result * mm_to_yd;
break;
}
return result;
}
break;
case "cm":
if(double.TryParse(values[0].ToString(), out result))
{
switch(values[2].ToString())
{
case "mm":
result = result * cm_to_mm;
break;
case "in":
result = result * cm_to_in;
break;
case "ft":
result = result * cm_to_ft;
break;
case "yd":
result = result * cm_to_yd;
break;
}
return result;
}
break;
case "in":
if(double.TryParse(values[0].ToString(), out result))
{
switch(values[2].ToString())
{
case "mm":
result = result * in_to_mm;
break;
case "cm":
result = result * in_to_cm;
break;
case "ft":
result = result * in_to_ft;
break;
case "yd":
result = result * in_to_yd;
break;
}
return result;
}
break;
case "ft":
if(double.TryParse(values[0].ToString(), out result))
{
switch(values[2].ToString())
{
case "mm":
result = result * ft_to_mm;
break;
case "cm":
result = result * ft_to_cm;
break;
case "in":
result = result * ft_to_in;
break;
case "yd":
result = result * ft_to_yd;
break;
}
return result;
}
break;
case "yd":
if(double.TryParse(values[0].ToString(), out result))
{
switch(values[2].ToString())
{
case "mm":
result = result * yd_to_mm;
break;
case "cm":
result = result * yd_to_cm;
break;
case "in":
result = result * yd_to_in;
break;
case "ft":
result = result * yd_to_ft;
break;
}
}
break;
}
}
return result;
//throw new NotImplementedException();
}
答案 0 :(得分：1)
textbox需要一个字符串，而不是double。
return result.ToString();
应该做到这一点。