CCCR：上下文命令、转换器和规则

new CommandAlpha (
  Context => {
    if (Context.GetCanExecute)
      Context.CanExecute = true;
    else
      MessageBox.Show(
        (Context.Parameter ?? "Alpha1-(NO PARAMs)").ToString()); } );

<DockPanel HorizontalAlignment="Stretch">
  <TextBlock Width="50">Target:</TextBlock>
  <TextBox x:Name="m_tTxt1"
    Text="{Binding
      ElementName=m_tTxt2,
      Path=Text,
      UpdateSourceTrigger=PropertyChanged,
      Converter={CCCR:ConverterBetaCSLambda Code=
        '(Context.IsBack ? &quot;Back: &quot; : &quot;Forward: &quot;) + (Context.In[0]).ToString()',
        NoExceptions=False}}"
      />
</DockPanel>
<DockPanel HorizontalAlignment="Stretch">
  <TextBlock Width="50">Source:</TextBlock>
  <TextBox x:Name="m_tTxt2"></TextBox>
</DockPanel>

C#

    private static CommandAlpha m_tCommandAlpha1;
    public static CommandAlpha CommandAlpha1 {
      get {
        if (m_tCommandAlpha1 == null)
          m_tCommandAlpha1 =
// Creating a command CommandAlpha, which to the request CanExecute always returns True,
// and displays a dialog box with the message given by parameter CommandParameter.
            new CommandAlpha (
              Context => {
                if (Context.GetCanExecute)
                  Context.CanExecute = true;
                else
                  MessageBox.Show(
                    (Context.Parameter ?? "Alpha1-(NO PARAMs)").ToString()); } );
        return m_tCommandAlpha1; } }

    private static CommandAlpha m_tCommandAlpha2;
    public static CommandAlpha CommandAlpha2 {
      get {
        if (m_tCommandAlpha2 == null)
// Creating a command CommandAlpha as above, but in a slightly different syntax.
          m_tCommandAlpha2 =
            new CommandAlpha (Context =>
              MessageBox.Show(!String.IsNullOrWhiteSpace(
               (Context.Parameter ?? "").ToString()) ?
                 Context.Parameter.ToString() : "Alpha2-(NO PARAMs)"))
                   { AlwaysCanExecute = true };
        return m_tCommandAlpha2; } }

    private static CommandBetaJS m_tCommandBetaJS1;
    public static CommandBetaJS CommandBetaJS1 {
      get {
        if (m_tCommandBetaJS1 == null)
// Creating of a command CommandBetaJS as before,
// but here a script is used instead of lambda expressions.
          m_tCommandBetaJS1 = 
            new CommandBetaJS (
              @"MessageBox.Show(!String.IsNullOrWhiteSpace(Context.Parameter) ?
                Context.Parameter : ""Beta1-(NO PARAMs)"")") { AlwaysCanExecute = true };
        return m_tCommandBetaJS1; } }

XAML

  <Window.Resources>
<!--
An entry into the window resource of simple command which displays a dialog box 
Request CanExecute is not served when the program starts, as
parameter AlwaysCanExecute is initialized in the "True".
-->
    <CCCR:CommandBetaJS
      x:Key="x_tCmd_MsgBox"
      Code="MessageBox.Show(Context.Parameter)"
      AlwaysCanExecute="True">
    </CCCR:CommandBetaJS>

<!--
An entry of ConverterBetaJS converter into the window resource
to convert String (in) to Integer and vice versa.
-->
    <CCCR:ConverterBetaJS x:Key="x_tCnv_JS_0_100" NoExceptions="True">
    <CCCR:ConverterBetaJS.Code>
      var c : ContextConverter = Context;
      if (!c.IsBack) {
        var n = int(c.In[0]);
        c.Out[0] = n.ToString(); }
      else {
        var n = Int32.Parse(c.In[0]);
        c.Out[0] = n; }
    </CCCR:ConverterBetaJS.Code>
    </CCCR:ConverterBetaJS>

<!--
This converter ConverterBetaCS is similar to the previous, but additionally
checks the CommandParameter and number on the membership
to the range of values [0, 100].
-->

    <CCCR:ConverterBetaCS x:Key="x_tCnv_CS_0_100" NoExceptions="False">
      <CCCR:ConverterBetaCS.Code>
        try {
          var c = Context;
          if (c.IsBack == ((c.Parameter ?? "").ToString() == "Slider")) {
            var n = Convert.ToInt32(c.In[0]);
            c.Out[0] = n.ToString(); }
          else {
            var s = (c.In[0] ?? "0").ToString().Trim();
            int n = 0;
            Int32.TryParse(s, out n);
            if (0 &gt; n || n &gt; 100)
              throw new Exception("Out of range [0; 100]!");
            c.Out[0] = n; } }
          catch (Exception e) {
            /*MessageBox.Show(e.Message);*/ }
      </CCCR:ConverterBetaCS.Code>
    </CCCR:ConverterBetaCS>

<!--
Style definition TextBox, to display Tooltips when there are validation errors
-->
   <Style x:Key="{x:Type TextBox}" TargetType="{x:Type TextBox}">
      <Style.Triggers>
        <Trigger Property="Validation.HasError" Value="True">
          <Setter Property="ToolTip"
            Value="{Binding RelativeSource={RelativeSource Self},
            Path=(Validation.Errors)[0].ErrorContent}"/>
          <Setter Property="Background" Value="Red"></Setter>
        </Trigger>
      </Style.Triggers>
    </Style>
    <Style x:Key="{x:Type Slider}" TargetType="{x:Type Slider}">
      <Style.Triggers>
        <Trigger Property="Validation.HasError" Value="True">
          <Setter Property="ToolTip"
            Value="{Binding RelativeSource={RelativeSource Self},
            Path=(Validation.Errors)[0].ErrorContent}"/>
          <Setter Property="Background" Value="Red"></Setter>
        </Trigger>
        <EventTrigger RoutedEvent="ValueChanged">
        </EventTrigger>
      </Style.Triggers>
    </Style>
  </Window.Resources>
  <Window.InputBindings>

<!--Binding commands to hotkeys.-->
    <KeyBinding Key="F1" Command="{x:Static local:WinMain.CommandAlpha1}"/>
    <KeyBinding Key="F2" Modifiers="Alt"  Command="{x:Static local:WinMain.CommandAlpha2}"/>
    <KeyBinding Key="F3" Command="{x:Static local:WinMain.CommandBetaJS1}"/>
    <KeyBinding Key="F4" Modifiers="Control"
      Command="{CCCR:CommandBetaVB 'System.Diagnostics.Process.Start((Context.Parameter))',
      AlwaysCanExecute=True, NoExceptions=True }"
      CommandParameter="calc.exe"/>
    <KeyBinding Key="F5"
      Command="{StaticResource x_tCmd_MsgBox}"
      CommandParameter="You pushed F5 key."/>
  </Window.InputBindings>

  <Grid Margin="10,10,10,10" >
    <StackPanel>
      <TextBlock TextWrapping="Wrap">
        The functionality except the one
      of the first three buttons on the left side is fully implemented in XAML.
      </TextBlock>
      <TextBlock TextWrapping="Wrap">
      That became possible by means of an anproach named
      <TextBlock Text="CCCR" FontWeight="Bold" /> (Context Commands, Converters and Rules)
      </TextBlock>

      <Grid Margin="0,6,0,0">
        <Grid.ColumnDefinitions>
          <ColumnDefinition Width="*"/>
          <ColumnDefinition Width="4"/>
          <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>

      <StackPanel Grid.Column="0">
        <TextBlock Margin="0,0,0,10"
        Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}">
        Hotkeys: F1, Alt+F2, F3, Ctrl+F4, F5
        </TextBlock>

<!--Binding a command of Alpha category (initialized in the main code)
to the button's Click event.-->
        <Button
          x:Name="m_tBtnAlpha1"
          HorizontalContentAlignment="Left"
          Content="Code / CommandAlpha : Show Message Box"
          CommandParameter="'This string is a parameter'"
          Command="{x:Static local:WinMain.CommandAlpha1}"
        />

<!--Binding a command of Alpha category (initialized in the main code)
to the button's Click event.-->
      <Button
        x:Name="m_tBtnAlpha2"
        HorizontalContentAlignment="Left"
        Content="Code / CommandAlpha : Show -//- (Shorter syntax)"
        CommandParameter="    "
        Command="{x:Static local:WinMain.CommandAlpha2}"
        />

<!--Binding a command of Beta category (initialized in the main code)
to the button's Click event.-->
      <Button
        x:Name="m_tBtnBetaJS1"
        HorizontalContentAlignment="Left"
        Content="Code / CommandBetaJS : Show -//-//-"
        CommandParameter="    "
        Command="{x:Static local:WinMain.CommandBetaJS1}"
        />


<!--Binding a command of Beta category (initialized in the window resources)
to the button's Click event.-->
      <Button
        HorizontalContentAlignment="Left"
        Content="XAML / CommandBetaJS : Show Message Box"
        Command="{StaticResource x_tCmd_MsgBox}"
        CommandParameter="Command Parameter ABRACADABRA"
        >
          </Button>

<!--
By the button's Click event a command in F# language is bound.
Pay attention to the use of the markup <system:String xml:space="preserve">
owing to the need to preserve the indentation from the left edge.
-->
      <Button
        HorizontalContentAlignment="Left"
        Content="XAML / CommandBetaFS : Run Notepad"
        CommandParameter="notepad.exe"
        >
        <Button.Command>
          <CCCR:CommandBetaFS
            AlwaysCanExecute="True">
              <CCCR:CommandBetaFS.Code>
                <system:String xml:space="preserve">
                  let s = Context.Parameter.ToString()
                  System.Diagnostics.Process.Start(s)
                </system:String>
              </CCCR:CommandBetaFS.Code>
            </CCCR:CommandBetaFS>
        </Button.Command>
      </Button>

<!--
By the button's Click event a command in VB.Net language is bound.
The launch of Calculator program is going.
-->
     <Button
        HorizontalContentAlignment="Left"
        Content="XAML / CommandBetaVB : Run Calculator"
        Command="{CCCR:CommandBetaVB 'System.Diagnostics.Process.Start(Context.Parameter.ToString())',
          AlwaysCanExecute=True, NoExceptions=True }"
        CommandParameter="calc.exe"
      />
          
<!--
By the button's Click event a command in the language of JS is bound. 
Error handling is demonstrated. Having set NoExceptions in False,
arising exceptions (Invoker) are passed further on to the stack calls.
Information about this exeption is also available in the property LastException.
-->
      <Button
            HorizontalContentAlignment="Left"
            Content="XAML / CommandBetaJS : NoExceptions=False"
            Command="{CCCR:CommandBetaJS 'fjh@#rt(y85h%$#93;',
              AlwaysCanExecute=True, NoExceptions=False }"
            CommandParameter="notepad.exe"
          />

<!--
By the button's Click event command in the language of JS is bound.
Error handling is demonstrated. Having installed NoExeptions in True,
arising exceptions in Invoker are intercepted, a recently emerged
exception is available in the property LastException.
-->
          <Button
            HorizontalContentAlignment="Left"
            Content="XAML / CommandBetaJS : NoExceptions=True"
            Command="{CCCR:CommandBetaJS 'fjh@#rt(y85h%$#9[u43',
              AlwaysCanExecute=True, NoExceptions=True }"
            CommandParameter="notepad.exe"
          />

<!--
By the button's Click event command in the language of VB is bound. 
Binding of a reference to the window to CommandParameter is Demonstrated.
The command closes the tied window.
-->
      <Button
          HorizontalContentAlignment="Left"
          Content="XAML / CommandBetaVB : Close Window"
          Command="{CCCR:CommandBetaVB 'Context.Parameter.Close()',
            AlwaysCanExecute=True, NoExceptions=False}"
          CommandParameter=
            "{Binding RelativeSource=
              {RelativeSource FindAncestor,
              AncestorType=local:WinMain, AncestorLevel=1}}"
          />

<!--
Command in JScript language is similar to the previous.
AlwaysCanExecute parameter was not defined, so the script
contains code to initialize ContextCommand.CanExecute
-->
      <Button
          HorizontalContentAlignment="Left"
          Content="XAML / CommandBetaJS : Close Window"
          CommandParameter=
            "{Binding RelativeSource=
             {RelativeSource FindAncestor,
             AncestorType=local:WinMain, AncestorLevel=1}}"
        >
        <Button.Command>
          <CCCR:CommandBetaJS>
            <CCCR:CommandBetaJS.Code>
              var v = Context;
                if (v.GetCanExecute)
                  v.CanExecute = true;
                else
                  v.Parameter.Close();
            </CCCR:CommandBetaJS.Code>
          </CCCR:CommandBetaJS>
        </Button.Command>
      </Button>

<!--
Command is in limited syntax of lambda expressions of C#.
Demonstrates the impossibility of invocation for the types not included in mscorlib.dll
-->
      <Button
          HorizontalContentAlignment="Left"
          Content="XAML / CommandBetaCSLambda : Close... (Exception)"
          Command="{CCCR:CommandBetaCSLambda 'w =&gt; w.CloseWindow()',
            AlwaysCanExecute=True, NoExceptions=False}"
          CommandParameter=
            "{Binding RelativeSource=
              {RelativeSource FindAncestor,
              AncestorType=local:WinMain, AncestorLevel=1}}"
        />

          <TextBlock Margin="0,10,0,0"
        Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}">
        ConverterBetaCSLambda: Source &lt;-&gt; Target</TextBlock>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Target:</TextBlock>
<!--
Converter in a limited syntax of lambda expressions in C#.
Demonstrates a possibility of a bidirectional exchange.
-->
        <TextBox x:Name="m_tTxt1"
          Text="{Binding
            ElementName=m_tTxt2,
            Path=Text,
            UpdateSourceTrigger=PropertyChanged,
            Converter={CCCR:ConverterBetaCSLambda Code=
              '(Context.IsBack ? &quot;Back: &quot; : &quot;Forward: &quot;) + (Context.In[0]).ToString()',
              NoExceptions=False}}"
            />
      </DockPanel>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Source:</TextBlock>
        <TextBox x:Name="m_tTxt2"></TextBox>
      </DockPanel>
      <TextBlock Margin="50,0,0,0" FontStyle="Italic">Change the contents of the textboxes</TextBlock>


        </StackPanel>

      <StackPanel Grid.Column="2">

<!--Example of usage of a combination of JS converter and C# validation rules.-->
      <TextBlock Margin="0,0,0,0"
        Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}">
      ConverterBetaJS + RuleBetaCS: TextBox &lt;-&gt; Slider</TextBlock>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Target:</TextBlock>
        <TextBox x:Name="m_tTxt3">
          <TextBox.Text>
            <Binding
              ElementName="m_tSlider1"
              Path="Value" Mode="TwoWay"
              UpdateSourceTrigger="PropertyChanged"
              Converter="{StaticResource x_tCnv_JS_0_100}">
<!--Creating of a validation rule of integer values in the range [0, 100].-->
              <Binding.ValidationRules>
                <CCCR:RuleBetaCS>
                  <CCCR:RuleBetaCS.Code>
                    var c = (ContextRule)Context;
                    var n = Int32.Parse(c.In[0].ToString());
                    if (n < 0 || n > 100)
                      throw new Exception("Out of range [0; 100]!");
                  </CCCR:RuleBetaCS.Code>
                </CCCR:RuleBetaCS>
              </Binding.ValidationRules>
            </Binding>
          </TextBox.Text>
        </TextBox>
      </DockPanel>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Source:</TextBlock>
        <Slider x:Name="m_tSlider1" Minimum="0" Maximum="100" Value="17"></Slider>
      </DockPanel>
      <TextBlock Margin="50,0,0,0" FontStyle="Italic">Play with text of the textbox. Tooltips.</TextBlock>

<!--Example of usage of the combination of C# Converter and JS validation rules.-->
      <TextBlock Margin="0,10,0,0"
        Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}">
      ConverterBetaCS + RuleBetaJS: Slider &lt;-&gt; TextBox</TextBlock>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Source:</TextBlock>
        <TextBox x:Name="m_tTxt4"/>
      </DockPanel>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Target:</TextBlock>
        <Slider x:Name="m_tSlider2" Minimum="0" Maximum="100">
          <Slider.Value>
            <Binding
              ElementName="m_tTxt4"
              Path="Text" Mode="TwoWay"
              ConverterParameter="Slider"
              UpdateSourceTrigger="PropertyChanged"
              Converter="{StaticResource x_tCnv_CS_0_100}"
              ValidatesOnExceptions="True">

<!--
Creating a rule validation integer values in the range [20, 80].
Pay attention to ValidatesOnExceptions="True" and UpdateSourceTrigger="PropertyChanged".
-->
              <Binding.ValidationRules>
                <CCCR:RuleBetaJS>
                  <CCCR:RuleBetaJS.Code>
                    var n = int(double(Context.In[0]));
                  if (n < 20 || n > 80)
                    throw new Exception("Slider is Out of range [20; 80]!");
                  </CCCR:RuleBetaJS.Code>
                </CCCR:RuleBetaJS>
              </Binding.ValidationRules>
            </Binding>
          </Slider.Value>
          <!---->
        </Slider>
      </DockPanel>
      <TextBlock Margin="50,0,0,0" FontStyle="Italic">
      Play with the slider (left/right edges). Tooltips.</TextBlock>

      <TextBlock Margin="0,10,0,0"
        Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}">
      ConverterBetaVB: Target <-> Four Sources</TextBlock>
      <DockPanel HorizontalAlignment="Stretch">
        <DockPanel.Resources>
          <CCCR:CommandBetaCS x:Key="x_tCmdUndo" 
            AlwaysCanExecute="True" NoExceptions="False">
<!--
Inserting into the DockPanel’s resource a command CommandBetaCS,
which finds in the text a symbol ';' cancels input.
-->
            <CCCR:CommandBetaCS.Code>
              var t=(TextBox)Context.In[0]; 
              var s=(string)Context.In[1]; 
              if (t.Text.Contains(s)) {
                Task.Factory.StartNew(() =>; {
                  t.Dispatcher.Invoke(
                    new Action(() => {
                      var sMsg = string.Format(
                        "The text contains '{0}' : \"{1}\"\n\nThe operation 'Undo' will be applied.", s, t.Text);
                      MessageBox.Show(sMsg, "CCCR:CommandBetaCS"); t.Undo(); }), null);
                    }); }
              else
                MessageBox.Show("Try to insert semicolons here!", "CCCR:CommandBetaCS");
            </CCCR:CommandBetaCS.Code>
          </CCCR:CommandBetaCS>
        </DockPanel.Resources>
        <TextBlock Width="50">Source 1:</TextBlock>
        <TextBox x:Name="m_tTxt5a" Text="Text1">
<!--Multiple binding to pass parameters to the command "x_tCmdUndo".-->
          <i:Interaction.Triggers>
            <i:EventTrigger EventName="TextChanged" >
              <i:InvokeCommandAction Command="{StaticResource x_tCmdUndo}">
                <i:InvokeCommandAction.CommandParameter>
                  <MultiBinding
                    Converter="{CCCR:ConverterBetaCS
                      Code='Context.Out[0] = new object[]{Context.In[0], Context.In[1]}'}">
                    <Binding
                      RelativeSource=
                        "{RelativeSource FindAncestor,
                         AncestorType=TextBox, AncestorLevel=1}"/>
                    <Binding>
                      <Binding.Source><system:String>;</system:String></Binding.Source>
                    </Binding>
                  </MultiBinding>
                </i:InvokeCommandAction.CommandParameter>
              </i:InvokeCommandAction>
            </i:EventTrigger>
          </i:Interaction.Triggers>
        </TextBox>
      </DockPanel>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Source 2:</TextBlock>
        <TextBox x:Name="m_tTxt5b" Text="Text2">
          <i:Interaction.Triggers>
            <i:EventTrigger EventName="TextChanged" >
<!-–Demonstrated the use of TriggerAction in VB.Net.-->
              <CCCR:ActionBetaVB 
                  Code="MessageBox.Show(&quot;Try insert semicolons into the 1st textbox.&quot;, &quot;CCCR:ActionBetaVB&quot;)"/>
              </i:EventTrigger>
          </i:Interaction.Triggers>
        </TextBox>
      </DockPanel>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Source 3:</TextBlock>
        <TextBox x:Name="m_tTxt5c" Text="Text3">
          <i:Interaction.Triggers>
            <i:EventTrigger EventName="TextChanged" >
<!-–Demonstrated the use of TriggerAction in VB.Net.-->
              <CCCR:ActionBetaVB 
                  Code="MessageBox.Show(&quot;Try insert semicolons into the 1st textbox.&quot;, &quot;CCCR:ActionBetaVB&quot;)"/>
            </i:EventTrigger>
          </i:Interaction.Triggers>
        </TextBox>
      </DockPanel>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Source 4:</TextBlock>
        <TextBox x:Name="m_tTxt5d" Text="Text4">
          <i:Interaction.Triggers>
            <i:EventTrigger EventName="TextChanged" >
              <CCCR:ActionBetaVB 
                  Code="MessageBox.Show(&quot;Try insert semicolons into the 1st textbox.&quot;, &quot;CCCR:ActionBetaVB&quot;)"/>
            </i:EventTrigger>
          </i:Interaction.Triggers>
        </TextBox>
      </DockPanel>
      <DockPanel HorizontalAlignment="Stretch">
        <TextBlock Width="50">Target:</TextBlock>
        <TextBox x:Name="m_tTxt7">
          <TextBox.Text>
            <MultiBinding UpdateSourceTrigger="PropertyChanged">
              <MultiBinding.Bindings>
                <Binding ElementName="m_tTxt5a" Path="Text"/>
                <Binding ElementName="m_tTxt5b" Path="Text"/>
                <Binding ElementName="m_tTxt5c" Path="Text"/>
                <Binding ElementName="m_tTxt5d" Path="Text"/>
              </MultiBinding.Bindings>
              <MultiBinding.Converter>
                <CCCR:ConverterBetaVB>
<!--Example of the use of Beta VB.Net converter in multiple two-way binding-->
                  <CCCR:ConverterBetaVB.Code>
                    <system:String xml:space="preserve">
                      Dim c = Context
                      If Not c.IsBack Then
                        Dim f = Function(i) i.ToString()
                        'c.Out(0) = String.Join(" ; ", c.In.Select(Function(i) i.ToString().Trim()))
                        c.Out(0) = String.Join(" ; ", (Enumerable.Select(Of Object, String)(c.In, Function(i) i.ToString().Trim())))
                      Else
                        Dim a = c.In(0).ToString().Split(";"C)
                        c.Out(0) = IIf((a.Length > 0), a(0).Trim(), "")
                        c.Out(1) = IIf((a.Length > 1), a(1).Trim(), "")
                        c.Out(2) = IIf((a.Length > 2), a(2).Trim(), "")
                        c.Out(3) = IIf((a.Length > 3), a(3).Trim(), "")
                      End If
                    </system:String>
                  </CCCR:ConverterBetaVB.Code>
                </CCCR:ConverterBetaVB>
              </MultiBinding.Converter>
            </MultiBinding>
          </TextBox.Text>
        </TextBox>
      </DockPanel>
      <TextBlock Margin="50,0,0,0" FontStyle="Italic">Change the contents of the textboxes</TextBlock>


    </StackPanel>
    </Grid>
    </StackPanel>
  </Grid>

注释

• Microsoft .NET Framework 4
• F# PowerPack
• Microsoft Expression Blend Software Development Kit (SDK) for .NET 4

结论

历史