Access Variable<int> in Custom Activity in WF4 - workflow-foundation-4

Question

I need to count how many times i iterate in a flowchart flow, but i need to be able to read and preferably write to the variable in a custom activity.
My current attempt is declaring the var in design view with scope of the entire Flowchart, default value 0 and incrementing using an Assign activity. But i cannot figure out how i can access the variable in a custom activity without resetting it.
My attempt to access the var is something like whats described in the answer here: Declare Variable<T> variable in a CodeActivity in windows workflow 4.0
Only i don't use a default value for the var when declaring though. Still it seems the var is not in any way related to the var i have defined in design view. I have also tried defining it in code only but then i cannot access it in for example a regular Assign activity.
So what can i do to be able to use the var as a "global" variable?
Thanks.

Answer 1

The most intuitive and perhaps correct way of doing it is to pass the variable that you're declaring on Flowchart level to inside your custom activity. Then you can do whatever you want with it's value and return it.
An example of a custom increment activity (this is how Assign activity works too):
public class IncrementActivity : CodeActivity<int>
{
[RequiredArgument]
public InArgument<int> CountVariable { get; set; }
protected override int Execute(CodeActivityContext context)
{
// Do whatever logic you want here
return CountVariable.Get(context) + 1;
}
}
Here it is a sample of usage using a Sequence (the same when using Flowchart):
var countVar = new Variable<int>("count");
var activity = new Sequence
{
Variables =
{
// declare counter variable at global scope
countVar
},
Activities =
{
new WriteLine { Text = new VisualBasicValue<string>(#"""Count: "" & count") },
new IncrementActivity { CountVariable = countVar, Result = countVar },
new WriteLine { Text = new VisualBasicValue<string>(#"""Count: "" & count") },
new IncrementActivity { CountVariable = countVar, Result = countVar },
new WriteLine { Text = new VisualBasicValue<string>(#"""Count: "" & count") },
new IncrementActivity { CountVariable = countVar, Result = countVar }
}
};
Output:
Count: 0
Count: 1
Count: 2
Note that is simpler through visual designer as you don't have to directly use VisualBasicValue<string> to build print string. Other than that, is exactly the same!