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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq.Expressions;
  4.  
  5. public class Test
  6. {
  7. 	public static void Main()
  8. 	{
  9. 		        // Getting types/methods
  10.         var queueItemType = typeof(double);
  11.         var queueType = typeof(Queue<>).MakeGenericType(queueItemType);
  12.         var queueEnqueueMethod = queueType.GetMethod(nameof(Queue<object>.Enqueue), new[] { queueItemType });
  13.  
  14.         // Build the Func<>
  15.         var result = Expression.Parameter(queueType, "result");
  16.  
  17.         var queueInstance = Expression.New(queueType);
  18.         var resultAssign = Expression.Assign(result, queueInstance);
  19.  
  20.         var queueItem = Expression.Constant(Convert.ChangeType(100, queueItemType), queueItemType);
  21.         var addCall = Expression.Call(result, queueEnqueueMethod, queueItem);
  22.  
  23.         var body = new List<Expression>
  24.         {
  25.             resultAssign,
  26.             addCall,
  27.             result  // The last line in body will be the result value of the Func<>.
  28.         };
  29.  
  30.         var lambda = Expression.Lambda<Func<Queue<double>>>(Expression.Block(new[] { result }, body));
  31.         var func = lambda.Compile();
  32.  
  33.         // Call it :-)
  34.         var queue = func();
  35.  
  36.         Console.WriteLine(queue.Count);
  37.         Console.WriteLine(queue.Dequeue());
  38. 	}
  39. }
Success #stdin #stdout 0.05s 134656KB
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https://ideone.com/wn5D4K
language:
C# (gmcs 5.20.1)
created:
5 years ago
visibility:
public

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