昨天我遇到了一个帖子,我想我有一个很好的解决方案。这里是http://www.blogs.intuidev.com/post/2011/01/02/combobox_autoopendropdown_attachedbehavior.aspx强制组合框下拉
我曾试图按照那个帖子的链接,因为我是一个新手,WPF和XAML我结束了一个奇怪的错误:Type ComboBox_ForceDropDown initialization failed. The type initializer for ERP_Lite.Views.DesignRelatedCode.ComboBox_ForceDropDown threw an exception.
这里是我的代码:
//ComboBox_ForceDropDown.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
namespace ERP_Lite.Views.DesignRelatedCode
{
public static class ComboBox_ForceDropDown
{
public static readonly DependencyProperty OpenDropDownAutomaticallyProperty = DependencyProperty.Register
(
"OpenDropDownAutomatically",
typeof(bool),
typeof(ComboBox_ForceDropDown),
new UIPropertyMetadata(false, onOpenDropDownAutomatically_Changed)
);
public static bool GetOpenDropDownAutomatically(ComboBox cbo)
{
return (bool)cbo.GetValue(OpenDropDownAutomaticallyProperty);
}
public static void SetOpenDropDownAutomatically(ComboBox cbo, bool value)
{
cbo.SetValue(OpenDropDownAutomaticallyProperty, value);
}
/// <summary>
/// Fired when the assignment of the behavior changes (IOW, is being turned on or off).
/// </summary>
private static void onOpenDropDownAutomatically_Changed(DependencyObject doSource, DependencyPropertyChangedEventArgs e)
{
//The ComboBox that is the target of the assignment
ComboBox cbo = doSource as ComboBox;
if (cbo == null)
return;
//Just to be safe ...
if (e.NewValue is bool == false)
return;
if ((bool)e.NewValue)
{
//Attach
cbo.GotFocus += cbo_GotFocus;
cbo.LostFocus += cbo_LostFocus;
}
else
{
//Detach
cbo.GotFocus -= cbo_GotFocus;
cbo.LostFocus -= cbo_LostFocus;
}
}
private static void cbo_GotFocus(object sender, RoutedEventArgs e)
{
//Open the DropDown/popup as soon as the control is focused
((ComboBox)sender).IsDropDownOpen = true;
}
private static void cbo_LostFocus(object sender, RoutedEventArgs e)
{
((ComboBox)sender).IsDropDownOpen = false;
}
}
}
而XAML文件
//App.xaml
<Application
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:comboFDD="clr-namespace:ERP_Lite.Views.DesignRelatedCode"
x:Class="ERP_Lite.App" StartupUri="Views/MainWindow.xaml">
<Application.Resources>
<!-- Resources scoped at the Application level should be defined here. -->
<Style TargetType="{x:Type ComboBox}">
<Setter Property="StaysOpenOnEdit" Value="True" />
<Setter Property="comboFDD:ComboBox_ForceDropDown.OpenDropDownAutomatically" Value="True"/> <!--I get error on this line-->
</Style>
</Application.Resources>
</Application>
这里是解决方案管理器的图像:
更新:内异常详细信息如下:
'ComboBox_ForceDropDown' type must derive from DependencyObject.
异常的详细信息可能会提供一些线索...... – makc
当你得到一个'Exception'这样,您可以点击弹出的链接'Window'称为'查看Details' 。如果你这样做了,另一个'Window'将打开所有'Exception'的细节。要特别注意'内部例外'。 – Sheridan