从类型动态获取类属性值

本文关键字：属性 获取 类型 动态 | 更新日期: 2023-09-27 17:55:03

我试图编写一个方法，查找具有特定自定义属性的程序集中的所有类型。我还需要能够提供一个字符串值匹配上。需要注意的是，我希望能够在任何类上运行此操作并返回任何值。

例如

:我想执行这样的调用

Type tTest = TypeFinder.GetTypesWithAttributeValue(Assembly.Load("MyAssembly"), typeof(DiagnosticTestAttribute), "TestName", "EmailTest");
到目前为止，我的方法是这样的: 
public static Type GetTypesWithAttributeValue(Assembly aAssembly, Type tAttribute, string sPropertyName, object oValue)
{
    object oReturn = null;
    foreach (Type type in aAssembly.GetTypes())
    {
        foreach (object oTemp in type.GetCustomAttributes(tAttribute, true))
        {
            //if the attribute we are looking for matches
            //the value we are looking for, return the current type.
        }
    }
    return typeof(string); //otherwise return a string type
}

我的属性看起来像这样:

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
public class DiagnosticTestAttribute : Attribute
{
    private string _sTestName = string.Empty;
    public string TestName
    {
        get { return _sTestName; }
    }
    public DiagnosticTest(string sTestName)
    {
        _sTestName = sTestName;
    }
}

对于那些熟悉表达式的人，我真的希望能够打出这样的呼叫:

TypeFinder.GetTypesWithAttributeValue<DiagnosticTestAttribute>(Assembly.Load("MyAssembly"), x=> x.TestName, "EmailTest");

其中表达式使用我的泛型类型来选择我要查找的属性。

从类型动态获取类属性值

应该可以:

public static Type GetTypeWithAttributeValue<TAttribute>(Assembly aAssembly, Func<TAttribute, object> pred, object oValue) {
  foreach (Type type in aAssembly.GetTypes()) {
    foreach (TAttribute oTemp in type.GetCustomAttributes(typeof(TAttribute), true)) {
      if (Equals(pred(oTemp), oValue)) {
        return type;
      }
    }
  }
  return typeof(string); //otherwise return a string type
}

或者更好:

public static Type GetTypeWithAttributeValue<TAttribute>(Assembly aAssembly, Predicate<TAttribute> pred) {
  foreach (Type type in aAssembly.GetTypes()) {
    foreach (TAttribute oTemp in type.GetCustomAttributes(typeof(TAttribute), true)) {
      if (pred(oTemp)) {
        return type;
      }
    }
  }
  return typeof(string); //otherwise return a string type
}

调用是这样的:

  GetTypeWithAttributeValue<DefaultValueAttribute>(Assembly.GetCallingAssembly(), attribute => attribute.Value,
                                                    "string");

和这个分别:

  GetTypeWithAttributeValue<DefaultValueAttribute>(Assembly.GetCallingAssembly(),
                                                    attribute => attribute.Value == "string");

很久以前，我开发了一些辅助方法来从表达式中提取属性名称，

我想这对你会有用的。

public static string Item<TItem, TMember>(this TItem obj, Expression<Func<TItem, TMember>> expression)
{
    if (expression.Body is MemberExpression)
    {
        return ((MemberExpression)(expression.Body)).Member.Name;
    }
    if (expression.Body is UnaryExpression)
    {
        return ((MemberExpression)((UnaryExpression)(expression.Body)).Operand).Member.Name;
    }
    if (expression.Body is ParameterExpression)
    {
        return expression.Body.Type.Name;
    }
    throw new InvalidOperationException();
}

相关文章：