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  1. using Microsoft.CSharp.RuntimeBinder;
  2. using System;
  3. using System.Dynamic;
  4. using System.Linq.Expressions;
  5.  
  6. namespace ConsoleApplication1
  7. {
  8.     public class ExpressionTreeUtils
  9.     {
  10.         private static Expression<Func<dynamic, decimal>> CreateLambdaCastExpression()
  11.         {
  12.             // source
  13.             var sourceParameterExpression = Expression.Parameter(typeof(object), "source");
  14.  
  15.             var binder = Binder.GetMember(
  16.                 CSharpBinderFlags.None, "IntProp", typeof(ExpressionTreeUtils),
  17.                 new[] { CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null) });
  18.  
  19.             // CSharpBinderFlags.ConvertExplicit: explicit cast 
  20.             // (will convert double to decimal)
  21.             // CSharpBinderFlags.None: implicit cast
  22.             // (will convert int to decimal)
  23.             var convert = Binder.Convert(CSharpBinderFlags.ConvertExplicit, typeof(decimal), typeof(ExpressionTreeUtils));
  24.  
  25.             // source.sourceProperty
  26.             var sourcePropertyExpression = Expression.Dynamic(
  27.                 binder, typeof(object), sourceParameterExpression);
  28.  
  29.             // (decimal) source;
  30.             var castedValueExpression = Expression.Dynamic(
  31.                 convert, typeof(decimal), sourcePropertyExpression);
  32.  
  33.             // () =>  (decimal) source;
  34.             return Expression.Lambda<Func<dynamic, decimal>>(castedValueExpression,
  35.                 sourceParameterExpression);
  36.         }
  37.  
  38.         public static void Test()
  39.         {
  40.             dynamic source = new ExpandoObject();
  41.             source.IntProp = 1.5;
  42.             decimal r = CreateLambdaCastExpression().Compile()(source);
  43.             Console.WriteLine(r);
  44.         }
  45.     }
  46.  
  47.     class Program
  48.     {
  49.         static void Main(string[] args)
  50.         {
  51.             ExpressionTreeUtils.Test();
  52.         }
  53.     }
  54. }
  55.  
Success #stdin #stdout 0.44s 30736KB
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1.5
https://ideone.com/VIf1h5
language:
C# (gmcs 5.20.1)
created:
8 years ago
visibility:
public

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