[英]MultiBinding Converter Not Displaying Results
學習正確地在WPF中使用綁定的過程中,我創建了一個小型轉換程序,將溫度,長度,分數轉換為小數等。將所有內容與溫度和分數配合都很好,因為這些都是通過簡單綁定完成的和轉換器。 我在長度轉換方面遇到了問題,因為它需要MultiBinding才能起作用。
對於控件,我使用兩個文本框表示原始長度和轉換后的長度。 它們中的每一個都有一個匹配的組合框,用戶可以在其中選擇度量單位(即厘米,英寸,毫米等)。
使用斷點,我確定條目將進入Convert方法,並且該方法中的代碼可以正確計算所有內容。 result
變量甚至在方法調用的末尾顯示正確轉換的數字,但是該數字不會使它返回到lengthResult
TextBox中。
我已經嘗試過所有可能想到的迭代,然后將其谷歌搜索了大約3個小時。 我找不到問題,也沒有找到足夠類似的情況的指南,無法解決該問題。 有人可以看看這個,找到我正在犯的(很可能)簡單的錯誤嗎?
注意:我在C#代碼中有一個ConvertBack
函數,但是除了默認throw new NotImplementedException
之外,它里面什么都沒有,所以我省略了它。 在Convert
首先工作之后,我會擔心這一點。 :)
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();
}
textbox
需要一個字符串,而不是double
。
return result.ToString();
應該做到的。
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