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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Reflection;
  4. using System.Linq;
  5. using System.Linq.Expressions;
  6.  
  7. public class Test
  8. {
  9. 	public static IEnumerable<T> SelectItems<T>(IEnumerable<T> items, string propName, string value)
  10. 	{
  11. 		IEnumerable<PropertyInfo> props;
  12. 		if (!string.IsNullOrEmpty(propName))
  13. 			props = new PropertyInfo[] { typeof(T).GetProperty(propName) };
  14. 		else
  15. 			props = typeof(T).GetProperties();
  16. 		props = props.Where(x => x != null && x.PropertyType == typeof(string));
  17. 		Expression lastExpr = null;
  18. 		ParameterExpression paramExpr = Expression.Parameter(typeof(T), "x");
  19. 		ConstantExpression valueExpr = Expression.Constant(value);
  20. 		foreach(var prop in props)
  21. 		{
  22. 			var propExpr = GetPropertyExpression(prop, paramExpr, valueExpr);
  23. 			if (lastExpr == null)
  24. 				lastExpr = propExpr;
  25. 			else
  26. 				lastExpr = Expression.MakeBinary(ExpressionType.Or, lastExpr, propExpr);
  27. 		}
  28. 		if (lastExpr == null)
  29. 			return new T[] {};
  30. 		var filterExpr = Expression.Lambda(lastExpr, paramExpr);
  31. 		return items.Where<T>((Func<T, bool>) filterExpr.Compile());
  32. 	}
  33.  
  34. 	private static Expression GetPropertyExpression(PropertyInfo prop, ParameterExpression paramExpr, ConstantExpression valueExpr)
  35. 	{
  36. 		var memberAcc = Expression.MakeMemberAccess(paramExpr, prop);
  37. 		var containsMember = typeof(string).GetMethod("Contains");
  38. 		return Expression.Call(memberAcc, containsMember, valueExpr);
  39. 	}
  40.  
  41. 	class TestClass
  42. 	{
  43. 		public string SomeProp { get; set; }
  44. 		public string SomeOtherProp { get; set; }
  45. 	}
  46.  
  47. 	public static void Main()
  48. 	{
  49. 		var data = new TestClass[] {
  50. 			new TestClass() { SomeProp = "AAA", SomeOtherProp = "BBB" }, 
  51. 			new TestClass() { SomeProp = "BBB", SomeOtherProp = "CCC" }, 
  52. 			new TestClass() { SomeProp = "CCC", SomeOtherProp = "AAA" }, 
  53. 		};
  54. 		var result = SelectItems(data, "", "A");
  55. 		foreach(var item in result)
  56. 			Console.WriteLine(item.SomeProp);
  57. 	}
  58. }
Success #stdin #stdout 0.09s 35480KB
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stdin
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Standard input is empty
stdout
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AAA
CCC
https://ideone.com/XE7rm7
language:
C# (gmcs 5.20.1)
created:
10 years ago
visibility:
public

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