11

我正在尝试编写一种方法来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来匹配。需要注意的是,我希望能够在任何类上运行它并返回任何值。

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,我的方法如下所示:

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
}

我的属性如下所示:

[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,我真的很想能够拨打这样的电话:

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

表达式使用我的泛型类型来选择我正在寻找的属性。

4

2 回答 2

14

这应该有效:

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
}

甚至更好:

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
}

这是调用的样子:

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

和这个分别:

  GetTypeWithAttributeValue<DefaultValueAttribute>(Assembly.GetCallingAssembly(),
                                                    attribute => attribute.Value == "string");
于 2013-01-21T17:18:00.903 回答
2

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,

我认为这对你有用。

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();
}

查看此文件了解更多信息。

于 2013-01-21T17:13:03.773 回答