Assuming the .resx file was added using Visual Studio under the project properties, there is an easier and less error prone way to access the string.
Accessing the string is then as easy as:
var resourceManager = JoshCodes.Core.Testing.Unit.Properties.Resources.ResourceManager;
var exampleXmlString = resourceManager.GetString("exampleXml");
Replace JoshCodes.Core.Testing.Unit
with the project's default namespace.