C# 如何在 WPF ComboBox 中使用 MultiBinding
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How to use MultiBinding in a WPF ComboBox
提问by Mike B
This is driving me NUTS!!!
这让我发疯了！！！
I have a ComboBoxused to filter a query by employee which works fine but only displays the employees first name. I want to use a MultiValueConverterto display the employees full name (This would be less urgent if we did not have 2 Mikes and 2 Daves)
我有一个ComboBox用于按员工过滤查询的方法，它工作正常，但只显示员工的名字。我想使用 aMultiValueConverter来显示员工的全名（如果我们没有 2 Mikes 和 2 Daves，这将不那么紧迫）
Below is my working code and the IMultiValueConverterClass (With unnecessary formatting trimmed out for brevity). I have tried everything I can think of to get the MultiConverter to work but I have had no luck.
下面是我的工作代码和IMultiValueConverter类（为简洁起见，删除了不必要的格式）。我已经尝试了所有我能想到的方法来让 MultiConverter 工作，但我没有运气。
<ComboBox ItemsSource="{Binding Path=EmployeesFilter}"
DisplayMemberPath="EmpFirstName"
SelectedValue="{Binding Path=EmployeeToShow, Mode=TwoWay}"/>
The ViewModel Properties it is bound to:
它绑定到的 ViewModel 属性：
// This collection is used to populate the Employee Filter ComboBox
private ObservableCollection<Employee> employeesFilter;
public ObservableCollection<Employee> EmployeesFilter
{
get {
return employeesFilter;
}
set {
if (employeesFilter != value)
{
employeesFilter = value;
OnPropertyChanged("EmployeesFilter");
}
}
}
// This property is TwoWay bound to the EmployeeFilters SelectedValue
private Employee employeeToShow;
public Employee EmployeeToShow
{
get {
return employeeToShow;
}
set {
if (employeeToShow != value)
{
employeeToShow = value;
OnPropertyChanged("EmployeeToShow");
QueryIssues(); // Requery with new employee filter
}
}
}
The IMultiValueConverter:
IMultiValueConverter：
class StringsToFullNameMultiConverter : IMultiValueConverter
{
public object Convert(object[] values,
Type targetType,
object parameter,
System.Globalization.CultureInfo culture)
{
// I added this because I kept getting DependecyProperty.UnsetValue
// Passed in as the program initializes
if (values[0] as string != null)
{
string firstName = (string)values[0];
string lastName = (string)values[1];
string fullName = firstName + " " + lastName;
return fullName;
}
return null;
}
public object[] ConvertBack(object value,
Type[] targetTypes,
object parameter,
System.Globalization.CultureInfo culture)
{
return null;
}
}
I tried a lot of different things but basically am using the following in the ComboBox
我尝试了很多不同的东西，但基本上是在 ComboBox 中使用以下内容
<ComboBox.SelectedValue>
<MultiBinding Converter="{StaticResource StringsToFullNameMultiConverter}"
Mode="OneWay" >
<Binding Path="EmpFirstName" />
<Binding Path="EmpLastName"/>
</MultiBinding>
</ComboBox.SelectedValue>
As it stands now the converter is called when the program initializes with the values set to DependencyProperty.UnsetValue. after that it is never called again, even when you select a name from the box. The names are still displayed as a first name.
就目前而言，当程序使用设置为 的值进行初始化时，将调用转换器DependencyProperty.UnsetValue。之后，即使您从框中选择一个名称，也不会再次调用它。名称仍显示为名字。
Thanks for any help or pointers to good tutorials/samples you can provide. All the ones I keep finding on the web are for textboxes and I can use them just fine all day.
感谢您提供任何帮助或指向好的教程/示例的指针。我在网上找到的所有文本框都是用于文本框的，我可以整天使用它们。
采纳答案by Josh
You're close! What you want to do though is ComboBox.ItemTemplate, not SelectedValue. Prepare for some XAML hell.
你很接近！你想要做的是ComboBox.ItemTemplate，而不是SelectedValue。为一些 XAML 地狱做好准备。
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource StringsToFillNameMultiConverter}">
<Binding Path="EmpFirstName" />
<Binding Path="EmpLastName" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
Also, if I recall correctly, you don't need to create your own converter if you're just formatting strings. I think you can do the following (someone please correct me if I'm wrong.)
另外，如果我没记错的话，如果您只是格式化字符串，则不需要创建自己的转换器。我认为您可以执行以下操作（如果我错了，请有人纠正我。）
<!-- "Last, First" -->
<MultiBinding StringFormat="{}{1}, {0}">
<Binding Path="EmpFirstName" />
<Binding Path="EmpLastName" />
</MultiBinding>
回答by Ian Ringrose
You may be better of using a data template for the items, so you have complete control over how each person is displayed in the dropdown list.
您最好为项目使用数据模板，这样您就可以完全控制每个人在下拉列表中的显示方式。
The type convert is OK provided you don't have a need to control the formatting of the different fields.
如果您不需要控制不同字段的格式，则类型转换是可以的。
回答by dba
I ended up by addig a Readonly Property to my Class and use Displaymemberpath in the Combobox
我最终将只读属性添加到我的类并在组合框中使用 Displaymemberpath
public class MyEmployee
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string DisplayName {
get { return FirstName + " " + LastName; }
}
}
Could something like this work for your situation...? BR, Daniel
这样的事情可以为您的情况工作......？BR，丹尼尔
