Assign a value to an attribute of a Microsoft.TeamFoundation.Build.Common.BuildParameter object using XAML - vb.net

Question

my BuildParameter is defined in my xaml build as follows:
<Activity this:Process.AdvancedBuildSettings=
"[New Microsoft.TeamFoundation.Build.Common.BuildParameter(
" { ""Attribute1"": """",
""Attribute2"": ""Value2"",
""Attribute3"": ""Value3"" } "
)]">
Now I want to update the value of Attribute1 of my BuildParameter but I can't figure out how to do it.
It doesn't look like I can use an Assign block because these attributes names are not known by the compiler, so I want to use BuildParameter's SetValue method but I'm not sure how to call this VB code in my xaml.
<Assign DisplayName="Update That Attribute">
<Assign.To>
<OutArgument x:TypeArguments="x:String">[AdvancedBuildSettings.Attribute1]</OutArgument><!-- this throws a compiler error because it doesn't know what Attribute1 is -->
</Assign.To>
<Assign.Value>
<InArgument x:TypeArguments="x:String">""NewValue""</InArgument>
</Assign.Value>
</Assign>

Answer 1

Not familiar with XAML, but here is a code snippet that using TFS API in C# to update the parameter name. You can use WorkflowHelpers.DeserializeProcessParameters Method and WorkflowHelpers.SerializeProcessParameters Method to get parameter name, remove it, and add the new parameter name, maybe it can help you something:
string argumentName = "Attribute1";
var process = Microsoft.TeamFoundation.Build.Workflow.WorkflowHelpers.DeserializeProcessParameters(BuildDefinition.ProcessParameters);
if (process.ContainsKey(argumentName))
{
process.Remove(argumentName);
process.Add(argumentName, attributeValue);
BuildDefinition.ProcessParameters = WorkflowHelpers.SerializeProcessParameters(process);
BuildDefinition.Save();
}

Answer 2

I was right, the "Assign" workflow tool was not the tool I wanted. I needed to use the "InvokeMethod" workflow tool in order to invoke the SetValue() method of my BuildParameter object in my XAML build.
MSDN InvokeMethod documentation
More details about the properties of InvokeMethod
So my solution looks like this:
<InvokeMethod DisplayName="Invoke That Method" MethodName="SetValue">
<InvokeMethod.GenericTypeArguments>
<x:Type Type="x:String" />
</InvokeMethod.GenericTypeArguments>
<InvokeMethod.TargetObject>
<InArgument x:TypeArguments="mtbc:BuildParameter">[AdvancedBuildSettings]</InArgument>
</InvokeMethod.TargetObject>
<InArgument x:TypeArguments="x:String">Attribute1</InArgument>
<InArgument x:TypeArguments="x:String">[NewValue]</InArgument>
</InvokeMethod>