Building Expression Trees and using Expression.Call method

Question

I have two dummy classes named TClass1 and TClass2. I would like to know how to build an expression tree to call the operation TClass1.TestMethod. I specifically have problem using Expression.Call method to create an expression based on instance methods of a class. Any help would be appreciated.

public class TClass1
{
    public string Prop1 { get; set; }
    public int Prop2 { get; set; }

    public TClass2 TestMethod(TClass2 tc2, int c)
    {
        return new TClass2() { Cprop1 = "The result: " + this.Prop1 + ".", Cprop2 = this.Prop2 * c };
    }
}

public class TClass2
{

    public string Cprop1 { get; set; }
    public int Cprop2 { get; set; }
}

Mic · Accepted Answer · 2011-12-19 11:02:39Z

11

Try this code:

var par1 = Expression.Parameter(typeof(TClass2), "tc2");
var par2 = Expression.Parameter(typeof(int), "c");
var instance = Expression.Parameter(typeof(TClass1), "inst");
var inExp = Expression.Call(instance,typeof(TClass1).GetMethod("TestMethod"),par1,par2);
var exp = Expression.Lambda<Func<TClass1,TClass2,int,TClass2>>(inExp,instance,
                                                                   par1,par2);
var deleg = exp.Compile();

answered Dec 19, 2011 at 11:02

Mic

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