Collection Activities in WF
Collection activities are used to work with collection objects in a workflow. .NET Framework 4.6.1 has system-provided activities for adding and removing items from a collection, testing for the existence of an item in a collection, and clearing a collection. ExistsInCollection and RemoveFromCollection have an OutArgument<T> of type Boolean, which indicates the result.
Important
If a collection activity is executed before setting the underlying collection object, an InvalidOperationException is thrown and the activity faults.
Collection activities
| Activity type | Description |
|---|---|
| AddToCollection<T> | Adds an item to a specified collection. |
| ClearCollection<T> | Clears all items from a specified collection. |
| ExistsInCollection<T> | Returns true if an item exists in a collection. |
| RemoveFromCollection<T> | Removes an item from a specified collection and returns true if the item was successfully removed. |
Using collection activities
The following code example demonstrates how to interact with a collection declared as a workflow variable. The collection used is a List<T> of String objects named fruitList.
Variable<ICollection<string>> fruitList = new Variable<ICollection<string>>
{
Default = new VisualBasicValue<ICollection<string>>("New List(Of String) From {\"Apple\", \"Orange\"}"),
Name = "FruitList"
};
Variable<bool> result = new Variable<bool>
{
Name = "Result"
};
Activity wf = new Sequence
{
Variables = { fruitList, result },
Activities =
{
new If
{
Condition = new ExistsInCollection<string>
{
Collection = fruitList,
Item = "Pear"
},
Then = new AddToCollection<string>
{
Collection = fruitList,
Item = "Pear"
},
Else = new RemoveFromCollection<string>
{
Collection = fruitList,
Item = "Apple"
}
},
new RemoveFromCollection<string>
{
Collection = fruitList,
Item = "Apple",
Result = result
},
new If
{
Condition = result,
Then = new ClearCollection<string>
{
Collection = fruitList,
}
}
}
};
<Sequence
xmlns="http://schemas.microsoft.com/netfx/2009/xaml/activities"
xmlns:scg="clr-namespace:System.Collections.Generic;assembly=mscorlib"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Sequence.Variables>
<x:Reference>__ReferenceID0</x:Reference>
<x:Reference>__ReferenceID1</x:Reference>
</Sequence.Variables>
<If>
<If.Condition>
<InArgument
x:TypeArguments="x:Boolean">
<ExistsInCollection
x:TypeArguments="x:String"
Item="Pear">
<ExistsInCollection.Result>
<OutArgument
x:TypeArguments="x:Boolean" />
</ExistsInCollection.Result>
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
<VariableValue.Variable>
<Variable
x:TypeArguments="scg:ICollection(x:String)"
x:Name="__ReferenceID0"
Default="[New List(Of String) From {"Apple", "Orange"}]"
Name="FruitList" />
</VariableValue.Variable>
</VariableValue>
</InArgument>
</ExistsInCollection>
</InArgument>
</If.Condition>
<If.Then>
<AddToCollection
x:TypeArguments="x:String"
Item="Pear">
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</AddToCollection>
</If.Then>
<If.Else>
<RemoveFromCollection
x:TypeArguments="x:String"
Item="Apple"
Result="{x:Null}">
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</RemoveFromCollection>
</If.Else>
</If>
<RemoveFromCollection
x:TypeArguments="x:String"
Item="Apple">
<RemoveFromCollection.Result>
<OutArgument
x:TypeArguments="x:Boolean">
<VariableReference
x:TypeArguments="x:Boolean">
<VariableReference.Result>
<OutArgument
x:TypeArguments="Location(x:Boolean)" />
</VariableReference.Result>
<VariableReference.Variable>
<Variable
x:TypeArguments="x:Boolean"
x:Name="__ReferenceID1"
Name="Result" />
</VariableReference.Variable>
</VariableReference>
</OutArgument>
</RemoveFromCollection.Result>
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</RemoveFromCollection>
<If>
<If.Condition>
<InArgument
x:TypeArguments="x:Boolean">
<VariableValue
x:TypeArguments="x:Boolean"
Variable="{x:Reference __ReferenceID1}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="x:Boolean" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</If.Condition>
<If.Then>
<ClearCollection
x:TypeArguments="x:String">
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</ClearCollection>
</If.Then>
</If>
</Sequence>
The above code samples can also be created using CSharpValue<TResult> instead of VisualBasicValue<TResult>
Variable<ICollection<string>> fruitList = new Variable<ICollection<string>>
{
Default = new CSharpValue<ICollection<string>>("new List<String> From {\"Apple\", \"Orange\"};"),
Name = "FruitList"
};
Variable<bool> result = new Variable<bool>
{
Name = "Result"
};
Activity wf = new Sequence
{
Variables = { fruitList, result },
Activities =
{
new If
{
Condition = new ExistsInCollection<string>
{
Collection = fruitList,
Item = "Pear"
},
Then = new AddToCollection<string>
{
Collection = fruitList,
Item = "Pear"
},
Else = new RemoveFromCollection<string>
{
Collection = fruitList,
Item = "Apple"
}
},
new RemoveFromCollection<string>
{
Collection = fruitList,
Item = "Apple",
Result = result
},
new If
{
Condition = result,
Then = new ClearCollection<string>
{
Collection = fruitList,
}
}
}
};
<Sequence
xmlns="http://schemas.microsoft.com/netfx/2009/xaml/activities"
xmlns:scg="clr-namespace:System.Collections.Generic;assembly=mscorlib"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Sequence.Variables>
<x:Reference>__ReferenceID0</x:Reference>
<x:Reference>__ReferenceID1</x:Reference>
</Sequence.Variables>
<If>
<If.Condition>
<InArgument
x:TypeArguments="x:Boolean">
<ExistsInCollection
x:TypeArguments="x:String"
Item="Pear">
<ExistsInCollection.Result>
<OutArgument
x:TypeArguments="x:Boolean" />
</ExistsInCollection.Result>
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
<VariableValue.Variable>
<Variable
x:TypeArguments="scg:ICollection(x:String)"
x:Name="__ReferenceID0"
Default="[new List<String> From {"Apple", "Orange"};]"
Name="FruitList" />
</VariableValue.Variable>
</VariableValue>
</InArgument>
</ExistsInCollection>
</InArgument>
</If.Condition>
<If.Then>
<AddToCollection
x:TypeArguments="x:String"
Item="Pear">
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</AddToCollection>
</If.Then>
<If.Else>
<RemoveFromCollection
x:TypeArguments="x:String"
Item="Apple"
Result="{x:Null}">
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</RemoveFromCollection>
</If.Else>
</If>
<RemoveFromCollection
x:TypeArguments="x:String"
Item="Apple">
<RemoveFromCollection.Result>
<OutArgument
x:TypeArguments="x:Boolean">
<VariableReference
x:TypeArguments="x:Boolean">
<VariableReference.Result>
<OutArgument
x:TypeArguments="Location(x:Boolean)" />
</VariableReference.Result>
<VariableReference.Variable>
<Variable
x:TypeArguments="x:Boolean"
x:Name="__ReferenceID1"
Name="Result" />
</VariableReference.Variable>
</VariableReference>
</OutArgument>
</RemoveFromCollection.Result>
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</RemoveFromCollection>
<If>
<If.Condition>
<InArgument
x:TypeArguments="x:Boolean">
<VariableValue
x:TypeArguments="x:Boolean"
Variable="{x:Reference __ReferenceID1}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="x:Boolean" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</If.Condition>
<If.Then>
<ClearCollection
x:TypeArguments="x:String">
<InArgument
x:TypeArguments="scg:ICollection(x:String)">
<VariableValue
x:TypeArguments="scg:ICollection(x:String)"
Variable="{x:Reference __ReferenceID0}">
<VariableValue.Result>
<OutArgument
x:TypeArguments="scg:ICollection(x:String)" />
</VariableValue.Result>
</VariableValue>
</InArgument>
</ClearCollection>
</If.Then>
</If>
</Sequence>
See also
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