How to create a variable / property in Wix and pass to it the value of using C#?

Question

How to create a variable / property in Wix and pass to it the value of using C#?

I am writing project installer and encountered a problem related to the transfer of value from C # ([CustomAction] Wix and Bootstrapper) to Wix Toolset 3.10. Both solutions do not work.

Solution 1: Using Wix Bootstrapper:

Bootstrapper.Engine.StringVariables["MyVariable"] = "test";

Solution 2: Using the Custom Actions: I create Bundle.wxs variable:

<Variable Name="MyVariable" Type="string" Value="" />

I set a property in the MSI Property, which should be the value of the variable "MyVariable":

<MsiProperty Name=" MYVARIABLE" Value="[MyVariable]" />

I create Product.wxs property:

<Property Id="MyVariable" Value="abcXYZ123" />

I create Product.wxs Custom Actions in which we set the property:

<CustomAction Id="MyVariable" Property="MyVariable" Value="[MyVariable]" />

I create a Custom Action in Product.wxs:

<CustomAction Id="Prefferences" 
          BinaryKey="MyCustomAction" 
          DllEntry="MySimpleAction"
          Execute="immediate" 
          Return="ignore" />

Performing during the installation process:

<InstallExecuteSequence>
  <Custom Action="Prefferences" After="InstallFiles">
    <![CDATA[Not Installed and Not Reinstall]]>
  </Custom>
</InstallExecuteSequence>

I create in class Custom Action.cs access to these properties:

[CustomAction]
    public static ActionResult MySimpleAction(Session session)
    {
        session["MyVariable"] = "Test przesłania parametru!";
        return ActionResult.Success;
    }

Both solution does not convey the text of the C # code to Wix.