How to conditionally use InvokeMethod in an XAML Windows workflow foundation

问题

In windows workflow foundation sequence workflow, How to use invoke method tags to be invoked based on certain condition?

For example,

<Sequence>
  <Sequence.Variables>
<Variable x:TypeArguments="x:String" Default="[&quot;this is an out param&quot;]" Name="outParam" />
  <Variable x:TypeArguments="x:Int32" Name="resultValue" />
  <Variable x:TypeArguments="msi:TestClass" Default="[New TestClass()]" Name="varTestClass" />
</Sequence.Variables>
<sap:WorkflowViewStateService.ViewState>
  <scg:Dictionary x:TypeArguments="x:String, s:Object">
    <x:Boolean x:Key="IsExpanded">True</x:Boolean>
  </scg:Dictionary>
</sap:WorkflowViewStateService.ViewState>
<WriteLine sap:VirtualizedContainerService.HintSize="299.663333333333,59.2766666666667" Text="[&quot;Instance method call&quot;]" />
<InvokeMethod DisplayName="Instance Method Call" sap:VirtualizedContainerService.HintSize="299.663333333333,127.553333333333" MethodName="InstanceMethod1">
  <InvokeMethod.TargetObject>
    <InArgument x:TypeArguments="msi:TestClass">[New TestClass()]</InArgument>
  </InvokeMethod.TargetObject>
</InvokeMethod>
<InvokeMethod DisplayName="Instance Method Call with Parameters" sap:VirtualizedContainerService.HintSize="299.663333333333,127.553333333333" MethodName="InstanceMethod">
  <InvokeMethod.TargetObject>
    <InArgument x:TypeArguments="msi:TestClass">[New TestClass()]</InArgument>
  </InvokeMethod.TargetObject>
  <InArgument x:TypeArguments="x:String">["My favorite number is"]</InArgument>
  <InArgument x:TypeArguments="x:Int32">42</InArgument>
</InvokeMethod>
</Sequence>

Suppose, I call the above activity, all the invoke methods will be triggered.

But what is needed, is something like,

<Sequence>
  <Sequence.Variables>
<Variable x:TypeArguments="x:String" Default="[&quot;this is an out param&quot;]" Name="outParam" />
  <Variable x:TypeArguments="x:Int32" Name="resultValue" />
  <Variable x:TypeArguments="msi:TestClass" Default="[New TestClass()]" Name="varTestClass" />
</Sequence.Variables>
<sap:WorkflowViewStateService.ViewState>
  <scg:Dictionary x:TypeArguments="x:String, s:Object">
    <x:Boolean x:Key="IsExpanded">True</x:Boolean>
  </scg:Dictionary>
</sap:WorkflowViewStateService.ViewState>
<WriteLine sap:VirtualizedContainerService.HintSize="299.663333333333,59.2766666666667" Text="[&quot;Instance method call&quot;]" />
//If (stateArgument =="created")
//{
<InvokeMethod DisplayName="Instance Method Call" sap:VirtualizedContainerService.HintSize="299.663333333333,127.553333333333" MethodName="InstanceMethod1">
  <InvokeMethod.TargetObject>
    <InArgument x:TypeArguments="msi:TestClass">[New TestClass()]</InArgument>
  </InvokeMethod.TargetObject>
</InvokeMethod>
//}
//else if(stateArguement == "running")
//{
<InvokeMethod DisplayName="Instance Method Call with Parameters" sap:VirtualizedContainerService.HintSize="299.663333333333,127.553333333333" MethodName="InstanceMethod">
  <InvokeMethod.TargetObject>
    <InArgument x:TypeArguments="msi:TestClass">[New TestClass()]</InArgument>
  </InvokeMethod.TargetObject>
  <InArgument x:TypeArguments="x:String">["My favorite number is"]</InArgument>
  <InArgument x:TypeArguments="x:Int32">42</InArgument>
</InvokeMethod>
//}
</Sequence>

Can someone give some idea how to go about this?

回答1:

You can use the If activity (in namespace System.Activities.Statements) for conditionally executing pieces of a workflow:

<If DisplayName="Invoke something based on a conditional" sap2010:WorkflowViewState.IdRef="If_1">
    <If.Condition>
        <InArgument x:TypeArguments="x:Boolean">
            <mca:CSharpValue x:TypeArguments="x:Boolean">1 == 2</mca:CSharpValue>
        </InArgument>
    </If.Condition>
    <If.Then>
        <InvokeMethod sap2010:WorkflowViewState.IdRef="InvokeMethod_1" MethodName="WriteSomething" TargetType="local:MyStatics" />
    </If.Then>
    <If.Else>
        <InvokeMethod sap2010:WorkflowViewState.IdRef="InvokeMethod_2" MethodName="WriteSomethingElse" TargetType="local:MyStatics" />
    </If.Else>
</If>

来源：https://stackoverflow.com/questions/37390601/how-to-conditionally-use-invokemethod-in-an-xaml-windows-workflow-foundation