Question

出于我的项目的目的，我需要对一个权限进行一些linq查询，我使用表达式工厂方法来构建动态过滤谓词。

考虑此代码：

public class mother{
  public int age {get; set;}
  public string name {get; set;}
  public child child {get; set;}
}

public class child{
  public int age {get; set;}
  public string name {get; set;}
}

//predicate builder
public static Expression<Func<T, bool>> GetChildNamePredicat<T>(){
  var param = Expression.Parameter(typeof(T), "param");

  // age property of mother class
  var motherAgeProperty = Expression.MakeMemberAccess(param, typeof(T).GetProperty("age"));

  // name property of child class
  var motherChildProperty = Expression.MakeMemberAccess(param, typeof (t).GetProperty("child"));
  var childNameProperty = Expression.MakeMemberAccess(motherChildProperty , typeof (child).GetProperty("name "));

   BinaryExpression motherAgeCondition;
   BinaryExpression childNameCondition;

  //building condition mother age >= 40 and child name = junior
  var motherAgeConst = Expression.Constant(40, typeof(int));
  var childNameConst = Expression.Constant("junior", typeof(string));
  motherAgeCondition = Expression.GreaterThanOrEqual(motherAgeProperty, motherAgeConst);
  childNameCondition= Expression.Equal(childNameProperty, childNameConst);
  var mergeCondition = Expression.AndAlso(motherAgeCondition , childNameCondition);

  //return expression
  return Expression.Lambda<Func<T, bool>>(mergeCondition , param);
}

var myPredicate = GetChildNamePredicat<mother>();

此代码编译成功，但似乎不是fonctionnal，没有结果...... 通过在“myPredicate”上使用变量的间谍，我可以看到这样的lambda调试视图：

.Lambda
#Lambda1<System.Func`2[myNameSpace.mother,System.Boolean]>(myNameSpace.mothe $e) { $e.age >= 40 &&  ($e.child).name == "junior" }

（$ e.child）......太奇怪了

您是否知道另一个解决方案或/并且想知道从母参数访问子名称属性？

提前谢谢！

使用linq表达式工厂方法访问成员属性

0 个答案: