与属性名作为字符串过滤的模板列表 [英] Filtering on template list with property name as string

问题描述

您好我要申请过滤器通用类。样本类如下：

Hi I have to apply filter on generic class. The sample class is as follows

public class Sample<T>
{
    List<T> sourceList = new List<T>();

    public void applyFilter(string propertyName , EnumOperator operator , object value)
    {

    }
}

在这里，我想使用LINQ或动态LINQ来实现过滤器，但我没有得到任何积极的方向来实现此功能。

Here I want to implement filter using linq or dynamic linq but am not getting any positive direction to implement this functionality.

请给我一些积极的方向，这样我可以实现这个功能。

Please give me some positive direction so that I can implement this functionality.

感谢。

推荐答案

我会建议返回一个过滤列表，而不是修改源，也是字符串经营者是一个C＃的关键字，因此该方法的签名可能是

I would recommend returning an filtered list instead of modifying the source, and also the string "operator" is a C# keyword, so the signature of the method could be:

public List<T> ApplyFilter(string propertyName, EnumOperator operatorType, object value)
{
   ....
}

我的假设 EnumOperator 是枚举有这样的价值观：

where I assume that the EnumOperator is an enum with values like this:

public enum EnumOperator
{
   Equal,
   NotEqual,
   Bigger,
   Smaller
}

和你有一些方法来检查，如果一个运营商的值通过或未能通过测试，沿着线的东西：

and that you have some way to check if for an operator a value passes or fails the test, something along the lines of:

public static class OperatorEvaluator
{ 
  public static bool Evaluate(EnumOperator operatorType, object first, object second)
  {
    ...
  }
}

鉴于这种情况，你可以这样做：

Given that, you can do something like:

public List<T> ApplyFilter(string propertyName , EnumOperator operatorType, object value)
{
  PropertyInfo pi = typeof(T).GetProperty(propertyName);
  List<T> result = sourceList.Where(item => { 
    var propValue = pi.GetValue(item, null);
    return OperatorEvaluator.Evaluate(operatorType, propValue, value);
  }).ToList();
  return result;
}

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这是说，你总是可以使用LINQ的方法，而不是诉诸反射过滤几乎所有的东西。

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That said, you can always use LINQ's methods to filter almost anything without resorting to reflection.

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