工作记录--WPF自定义控件，实现一个可设置编辑模式的TextBox

1. 背景

　　因为最近在使用wpf开发桌面端应用，在查看页面需要把TextBox和Combox等控件设置为只读的。原本是个很简单的事，设置属性IsReadOnly="True"或IsEnabled="False"就可以解决了，可是产品觉得样式不是他想要的（背景是灰色的），想要实现的效果是和编辑时的样式一致，仅仅是不可编辑而已。我想这也简单啊，强制修改背景色和字体就完事了，结果发现TextBox修改背景色是可行的，但是修改后字体是灰色的，改也改不了，Combox更是连背景色都改不了。。。wtf

　　于是开始了一段Google之路，发现别人说的都好复杂，大概明白了修改自带的不可编辑或只读的样式不是一件简单的事。于是我准备用一种变通的方法来解决这个问题，写个自定义控件，通过设置自定义控件的属性来显示/隐藏内部控件的方式。

2. 实现

　　首先新建一个用户控件（UserControl），命名为LabelRenderTextBox，在LabelRenderTextBox.xaml文件编写以下内容　

　  <!--DataContext="{Binding RelativeSource={RelativeSource self}} datacontext绑定自身会破坏binding链，而通过第一个child来binding则不会破坏"-->
　　<StackPanel x:Name="panel" DataContext="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=local:LabelRenderTextBox}}">
<Border BorderThickness="1" BorderBrush="#ccc" x:Name="label" Width="{Binding ElementName=panel, Path=ActualWidth}" Height="24" Visibility="Collapsed" Padding="5,3,0,0">
<TextBlock Text="{Binding Text}" ></TextBlock>
</Border>
<TextBox x:Name="textbox" Text="{Binding Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="{Binding ElementName=panel, Path=ActualWidth}" Height="24"
base:CustomizeProperty.Placeholder="{Binding Placeholder}" TextChanged="Textbox_TextChanged" ></TextBox>
</StackPanel>

　　如图，panel是UserControl内部最外层的元素，把这里的DataContext设为自身，就可以把内部控件的属性和cs文件中的属性进行绑定。label是默认隐藏的元素，textbox是默认显示的控件。label和textbox的Text属性都是绑定的LabelRenderTextBox的Text属性，宽度都是和最外层的panel的宽度进行绑定的，以便于使用者自己设置宽度。

　　那么当我们使用LabelRenderTextBox控件进行编辑的时候，实际上还是通过TextBox来实现了，因为设置了Mode=TwoWay进行了双向绑定，UpdateSourceTrigger=PropertyChanged，所以当TextBox的Text改变时，LabelRenderTextBox的Text值也会跟着改变，所以我们可以在LabelRenderTextBox.cs文件里添加一个属性 public string Text { get; set; } ，可是当我们在外部直接修改LabelRenderTextBox的Text值如何使内部的TextBox值也跟着改变呢？这时候就需要用到wpf的依赖属性了，首先通过查看UserControl的继承关系可以发现UserControl是继承自DependencyObject的，意味着它是一个依赖对象，可以设置依赖属性。所以我们可以在LabelRenderTextBox.cs文件里添加以下代码：

public string Text { get
{
return (string)this.GetValue(TextProperty);
}
set
{
this.SetValue(TextProperty, value);
}
}

public static readonly DependencyProperty TextProperty =
DependencyProperty.RegisterAttached("Text", typeof(string), typeof(LabelRenderTextBox), new PropertyMetadata("", OnTextChanged));

private static void OnTextChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.Text = e.NewValue as string;
}
}

　　通过DependencyProperty.RegisterAttached方法注册一个Text属性，string类型的，类型为LabelRenderTextBox，PropertyMetadata的第一个参数是默认值，第二个参数是一个回调函数（当属性改变时进行回调），回调时通过Text的set方法来调用SetValue属性来设置依赖属性的值并通知与其绑定的属性（想知道如何实现的可以参考：WPF依赖对象（DependencyObject） 实现源码，理解WPF原理必读）。

　　接下来，定义一个枚举类来列举出需要的编辑模式，我这里列举出4种模式，可根据自己的需求进行调整。

public enum EditModes
{
//编辑模式
Editable = 0,
//只读模式
ReadOnly = 1,
//只读模式展示，单击进入编辑模式，失去焦点后恢复只读模式
Click = 2,
//只读模式展示，双击进入编辑模式，失去焦点后恢复只读模式
DoubleCLick = 3
}

　　定义了枚举之后就要使用了，和设置Text属性的方式来注册一个EditMode依赖属性，SetEditable方法传入true/false来设置textbox（编辑）和label（只读）的显示和隐藏。这样只要通过设置EditMode属性就可以完美实现产品的需求了，我真棒！

　　#region EditModeProperty
public EditModes EditMode {
get { return (EditModes)this.GetValue(EditModeProperty); }
set {
this.SetValue(EditModeProperty, value);
if (value == EditModes.Editable)
{
SetEditable(true);
}
else
{
SetEditable(false);
}
}
}

public static readonly DependencyProperty EditModeProperty =
DependencyProperty.RegisterAttached("EditMode", typeof(EditModes), typeof(LabelRenderTextBox), new PropertyMetadata(EditModes.Editable, OnEditModeChanged));

private static void OnEditModeChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.EditMode = (EditModes)e.NewValue;
}
}
#endregion

private void SetEditable(bool editable)
{
if (editable)
{
this.label.Visibility = Visibility.Collapsed;
this.textbox.Visibility = Visibility.Visible;
}
else
{
this.label.Visibility = Visibility.Visible;
this.textbox.Visibility = Visibility.Collapsed;
}
}

　　可是按照产品的需求只要Editable和ReadOnly两个属性就够了，其他两个是用来扩展的，可以在合适的场景下带来更好的用户体验，默认展示只读模式，单击或者双击变为编辑模式，失去焦点后恢复只读模式。实现方法也很简单，直接在UserControl定义几个事件，在对应的事件函数进行如下处理。

　　 private void Click(object sender, MouseButtonEventArgs e)
{
if (EditMode == EditModes.Click)
SetEditable(true);
}

private void DoubleClick(object sender, MouseButtonEventArgs e)
{
if (EditMode == EditModes.DoubleCLick)
SetEditable(true);
}

private void Lost_Focus(object sender, RoutedEventArgs e)
{
if(EditMode == EditModes.DoubleCLick || EditMode == EditModes.Click)
SetEditable(false);
}

　　你可能会想，如果想监听TextBox的事件该怎么做呢，也很简单，在cs文件里定义相同的事件，然后在cs文件里监听对应事件，触发时调用定义的事件即可。

public event TextChangedEventHandler TextChanged;

private void Textbox_TextChanged(object sender, TextChangedEventArgs e)
{
this.TextChanged?.Invoke(this, e);
}

　　是不是很简单呢？希望可以帮到遇到相同问题的朋友，完整代码如下：

<UserControl x:Class="YZ.HIS.UserControls.LabelRenders.LabelRenderTextBox"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:base="clr-namespace:APP_YFT.Base;assembly=APP-YFT.Base"
xmlns:local="clr-namespace:YZ.HIS.UserControls.LabelRenders"
mc:Ignorable="d" BorderThickness="0"
Height="24" d:DesignWidth="80" PreviewMouseLeftButtonDown="Click" PreviewMouseDoubleClick="DoubleClick"
LostFocus="Lost_Focus">
<UserControl.Resources>
<Style x:Key="mySearchTextBoxStyle" TargetType="{x:Type TextBox}">
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Padding" Value="6,0,0,0"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Border x:Name="bdRoot"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
Background="{TemplateBinding Background}">
<DockPanel LastChildFill="True">
<Button x:Name="ClearButton"
DockPanel.Dock="Right"
Focusable="False"  Click="ExecCleanSearchText"
Width="{Binding ActualHeight, RelativeSource={RelativeSource Self}}"
FontSize="{TemplateBinding FontSize}">
<Button.Template>
<ControlTemplate>
<Image x:Name="Image" Source="/YZ.HIS;component/Images/tbClean_icon.png" Stretch="None"/>
</ControlTemplate>
</Button.Template>
</Button>
<ScrollViewer x:Name="PART_ContentHost" DockPanel.Dock="Left" Background="{TemplateBinding Background}"/>
</DockPanel>
</Border>
<ControlTemplate.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Text}" Value="">
<Setter TargetName="ClearButton" Property="Visibility" Value="Collapsed" />
</DataTrigger>
<Trigger Property="IsFocused" Value="True">
<Setter TargetName="bdRoot" Property="BorderBrush" Value="#569DE5"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="bdRoot" Property="BorderBrush" Value="#7EB4EA"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</UserControl.Resources>
<!--DataContext="{Binding RelativeSource={RelativeSource self}} datacontext绑定自身会破坏binding链，而通过第一个child来binding则不会破坏"-->
<StackPanel x:Name="panel" DataContext="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=local:LabelRenderTextBox}}">
<Border BorderThickness="1" BorderBrush="#ccc" x:Name="label" Width="{Binding ElementName=panel, Path=ActualWidth}" Height="24" Visibility="Collapsed" Padding="5,3,0,0">
<TextBlock Text="{Binding Text}" ></TextBlock>
</Border>
<TextBox x:Name="textbox" Text="{Binding Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="{Binding ElementName=panel, Path=ActualWidth}" Height="24"
base:CustomizeProperty.Placeholder="{Binding Placeholder}" TextChanged="Textbox_TextChanged" ></TextBox>
</StackPanel>
</UserControl>

using APP_YFT.Base;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace YZ.HIS.UserControls.LabelRenders
{
/// <summary>
/// LabelRenderTextBox.xaml 的交互逻辑
/// </summary>
public partial class LabelRenderTextBox : UserControl
{
public LabelRenderTextBox()
{
InitializeComponent();
}

#region events
public event TextChangedEventHandler TextChanged;

private void Textbox_TextChanged(object sender, TextChangedEventArgs e)
{
if (RequiredValue == RequiredValues.Number)
{
TextBox textBox = sender as TextBox;
string text = textBox.Text;
Regex reg = new Regex(@"^[0-9]*$");
if (text == null || (text.Count() == 0) || !reg.IsMatch(text))
{
textBox.Text = "";
return;
}
}
this.TextChanged?.Invoke(this, e);
}

//清空输入框事件
private void ExecCleanSearchText(object sender, RoutedEventArgs e)
{
Button btn = sender as Button;
if (btn == null)
return;
TextBox tb = btn.TemplatedParent as TextBox;
if (tb != null)
{
tb.Text = "";
}
}

private void Click(object sender, MouseButtonEventArgs e)
{
if (EditMode == EditModes.Click)
SetEditable(true);
}

private void DoubleClick(object sender, MouseButtonEventArgs e)
{
if (EditMode == EditModes.DoubleCLick)
SetEditable(true);
}

private void Lost_Focus(object sender, RoutedEventArgs e)
{
if(EditMode == EditModes.DoubleCLick || EditMode == EditModes.Click)
SetEditable(false);
}
#endregion

#region TextProperty
//public string Text { get; set; }
public string Text { get
{
return (string)this.GetValue(TextProperty);
}
set
{
this.SetValue(TextProperty, value);
}
}

public static readonly DependencyProperty TextProperty =
DependencyProperty.RegisterAttached("Text", typeof(string), typeof(LabelRenderTextBox), new PropertyMetadata("", OnTextChanged));

private static void OnTextChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.Text = e.NewValue as string;
}
}
#endregion

#region PlaceholderProperty
public string Placeholder { get
{
return (string)this.GetValue(PlaceholderProperty);
}
set
{
this.SetValue(PlaceholderProperty, value);
}
}

public static readonly DependencyProperty PlaceholderProperty =
DependencyProperty.RegisterAttached("Placeholder", typeof(string), typeof(LabelRenderTextBox), new PropertyMetadata("", OnPlaceholderChanged));

private static void OnPlaceholderChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.Placeholder = e.NewValue as string;
}
}
#endregion

#region RequiredValueProperty
public RequiredValues RequiredValue
{
get { return (RequiredValues)this.GetValue(RequiredValueProperty); }
set
{
this.SetValue(RequiredValueProperty, value);
}
}

public static readonly DependencyProperty RequiredValueProperty =
DependencyProperty.RegisterAttached("RequiredValue", typeof(RequiredValues), typeof(LabelRenderTextBox), new PropertyMetadata(RequiredValues.String, OnRequiredValueChanged));

private static void OnRequiredValueChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.RequiredValue = (RequiredValues)e.NewValue;
}
}
#endregion

#region UseSearchProperty
public bool UseSearch
{
get { return (bool)this.GetValue(UseSearchProperty); }
set
{
this.SetValue(UseSearchProperty, value);
if (value)
this.textbox.Style = this.FindResource("mySearchTextBoxStyle") as Style;

}
}

public static readonly DependencyProperty UseSearchProperty =
DependencyProperty.RegisterAttached("UseSearch", typeof(bool), typeof(LabelRenderTextBox), new PropertyMetadata(false, OnUseSearchChanged));

private static void OnUseSearchChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.UseSearch = (bool)e.NewValue;
}
}
#endregion

#region CaretIndexProperty
public int CaretIndex {
get { return (int)this.GetValue(CaretIndexProperty); }
set
{
this.SetValue(CaretIndexProperty, value);
this.textbox.CaretIndex = value;
}
}

public static readonly DependencyProperty CaretIndexProperty =
DependencyProperty.RegisterAttached("CaretIndex", typeof(int), typeof(LabelRenderTextBox), new PropertyMetadata(0, OnCaretIndexChanged));

private static void OnCaretIndexChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.CaretIndex = (int)e.NewValue;
}
}
#endregion

#region SelectionStartProperty
public int SelectionStart
{
get { return (int)this.GetValue(SelectionStartProperty); }
set
{
this.SetValue(SelectionStartProperty, value);
this.textbox.SelectionStart = value;
}
}

public static readonly DependencyProperty SelectionStartProperty =
DependencyProperty.RegisterAttached("SelectionStart", typeof(int), typeof(LabelRenderTextBox), new PropertyMetadata(0, OnSelectionStartChanged));

private static void OnSelectionStartChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.SelectionStart = (int)e.NewValue;
}
}
#endregion

#region EditModeProperty
public EditModes EditMode {
get { return (EditModes)this.GetValue(EditModeProperty); }
set {
this.SetValue(EditModeProperty, value);
if (value == EditModes.Editable)
{
SetEditable(true);
}
else
{
SetEditable(false);
}
}
}

public static readonly DependencyProperty EditModeProperty =
DependencyProperty.RegisterAttached("EditMode", typeof(EditModes), typeof(LabelRenderTextBox), new PropertyMetadata(EditModes.Editable, OnEditModeChanged));

private static void OnEditModeChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var element = obj as LabelRenderTextBox;
if (element != null)
{
element.EditMode = (EditModes)e.NewValue;
}
}
#endregion

private void SetEditable(bool editable)
{
if (editable)
{
this.label.Visibility = Visibility.Collapsed;
this.textbox.Visibility = Visibility.Visible;
}
else
{
this.label.Visibility = Visibility.Visible;
this.textbox.Visibility = Visibility.Collapsed;
}
}

}

public enum EditModes
{
//编辑模式
Editable = 0,
//只读模式
ReadOnly = 1,
//只读模式展示，单击进入编辑模式，失去焦点后恢复只读模式
Click = 2,
//只读模式展示，双击进入编辑模式，失去焦点后恢复只读模式
DoubleCLick = 3
}

public enum RequiredValues
{
String = 0,
Number = 1
}
}