Expression.Call and "Ambiguous Match Found"

I'm trying to write an expression that will call ToString on a property and assign it's value to a local variable. However, calling ToString on a object instance w/ an overload of ToString, causes an exception of "Ambigous Match Found" to be thrown. Here's an example:

var result = Expression.Variable(typeof(string), "result");
var matchTypeParameter = Expression.Parameter(typeof(MatchType), "matchType");
var targetProperty = Expression.Property(leadParameter开发者_如何学C, target);

var exp = Expression.Block(
  //Add the local current value variable
  new[] { result },

  //Get the target value
  Expression.Assign(result, Expression.Call(targetProperty, typeof(string).GetMethod("ToString"), null))

);

How can I call ToString if the instance has overloads for it? Thanks!

---

Replace:

typeof(string).GetMethod("ToString")

With:

typeof(string).GetMethod("ToString", Type.EmptyTypes)

In other words, get the method named "ToString" that takes zero arguments (empty type array).