c# Assembly.Load Not loading file (Windows 10)

I am using the new mef 2.0 framework however I am having issues loading an Assembly by name. I want to load the assembly by name, and not the path. Could someone point me in the right direction. I am using windows 10 operating system.

private void frmMef2UnitTest_Load(object sender, EventArgs e)
{
ComposeParts();
}

static void ComposeParts()
{
IList<Assembly> assemblies = new List<Assembly>(3);
var executingAssembly = Assembly.GetExecutingAssembly();
assemblies.Add(Assembly.GetExecutingAssembly());

assemblies.Add(Assembly.Load("HelloWorld")); // I get the error at this line

var loader = new MefLoader(assemblies);
loader.ComposeAllParts();
}