C#通过反射实例化对象

public static IPDFProvider Get(string vt)
{
IPDFProvider r = null;
Type tt = Type.GetType(vt);
ConstructorInfo ci = tt.GetConstructor(System.Type.EmptyTypes);
r = ci.Invoke(null) as IPDFProvider;
return r;
}

public static IPDFProvider Get(string path,string vt)
{
System.Reflection.Assembly ass = System.Reflection.Assembly.LoadFile(path);
//string vt = "Laptop.Order.PDF.WABPdfProvider2";
Laptop.Order.PDF.IPDFProvider r = null;
Type tt = ass.GetType(vt);
ConstructorInfo ci = tt.GetConstructor(System.Type.EmptyTypes);
r = ci.Invoke(null) as Laptop.Order.PDF.IPDFProvider;
return r;
}