我试图在我的代码中使用Reflection1示例实现数据转换。

GetSourceValue函数有一个比较各种类型的开关,但我想删除这些类型和属性,并让GetSourceValue只使用一个字符串作为参数来获取属性的值。我想在字符串中传递一个类和属性,并解析属性的值。

这可能吗?

1原始博客文章的Web存档版本


当前回答

以下是我根据其他答案得出的结论。把错误处理弄得这么具体,有点过分了。

public static T GetPropertyValue<T>(object sourceInstance, string targetPropertyName, bool throwExceptionIfNotExists = false)
{
    string errorMsg = null;

    try
    {
        if (sourceInstance == null || string.IsNullOrWhiteSpace(targetPropertyName))
        {
            errorMsg = $"Source object is null or property name is null or whitespace. '{targetPropertyName}'";
            Log.Warn(errorMsg);

            if (throwExceptionIfNotExists)
                throw new ArgumentException(errorMsg);
            else
                return default(T);
        }

        Type returnType = typeof(T);
        Type sourceType = sourceInstance.GetType();

        PropertyInfo propertyInfo = sourceType.GetProperty(targetPropertyName, returnType);
        if (propertyInfo == null)
        {
            errorMsg = $"Property name '{targetPropertyName}' of type '{returnType}' not found for source object of type '{sourceType}'";
            Log.Warn(errorMsg);

            if (throwExceptionIfNotExists)
                throw new ArgumentException(errorMsg);
            else
                return default(T);
        }

        return (T)propertyInfo.GetValue(sourceInstance, null);
    }
    catch(Exception ex)
    {
        errorMsg = $"Problem getting property name '{targetPropertyName}' from source instance.";
        Log.Error(errorMsg, ex);

        if (throwExceptionIfNotExists)
            throw;
    }

    return default(T);
}

其他回答

jheddings的回答很好。我想通过允许引用聚集的数组或对象的集合来改进它,这样propertyName可以是property1.property2[X].property3:

    public static object GetPropertyValue(object srcobj, string propertyName)
    {
        if (srcobj == null)
            return null;

        object obj = srcobj;

        // Split property name to parts (propertyName could be hierarchical, like obj.subobj.subobj.property
        string[] propertyNameParts = propertyName.Split('.');

        foreach (string propertyNamePart in propertyNameParts)
        {
            if (obj == null)    return null;

            // propertyNamePart could contain reference to specific 
            // element (by index) inside a collection
            if (!propertyNamePart.Contains("["))
            {
                PropertyInfo pi = obj.GetType().GetProperty(propertyNamePart);
                if (pi == null) return null;
                obj = pi.GetValue(obj, null);
            }
            else
            {   // propertyNamePart is areference to specific element 
                // (by index) inside a collection
                // like AggregatedCollection[123]
                //   get collection name and element index
                int indexStart = propertyNamePart.IndexOf("[")+1;
                string collectionPropertyName = propertyNamePart.Substring(0, indexStart-1);
                int collectionElementIndex = Int32.Parse(propertyNamePart.Substring(indexStart, propertyNamePart.Length-indexStart-1));
                //   get collection object
                PropertyInfo pi = obj.GetType().GetProperty(collectionPropertyName);
                if (pi == null) return null;
                object unknownCollection = pi.GetValue(obj, null);
                //   try to process the collection as array
                if (unknownCollection.GetType().IsArray)
                {
                    object[] collectionAsArray = unknownCollection as object[];
                    obj = collectionAsArray[collectionElementIndex];
                }
                else
                {
                    //   try to process the collection as IList
                    System.Collections.IList collectionAsList = unknownCollection as System.Collections.IList;
                    if (collectionAsList != null)
                    {
                        obj = collectionAsList[collectionElementIndex];
                    }
                    else
                    {
                        // ??? Unsupported collection type
                    }
                }
            }
        }

        return obj;
    }

添加到任何类:

public class Foo
{
    public object this[string propertyName]
    {
        get { return this.GetType().GetProperty(propertyName).GetValue(this, null); }
        set { this.GetType().GetProperty(propertyName).SetValue(this, value, null); }
    }

    public string Bar { get; set; }
}

然后,你可以使用as:

Foo f = new Foo();
// Set
f["Bar"] = "asdf";
// Get
string s = (string)f["Bar"];

在. net Standard中调用的方法已经改变(从1.6开始)。我们还可以使用c# 6的空条件操作符。

using System.Reflection; 
public static object GetPropValue(object src, string propName)
{
    return src.GetType().GetRuntimeProperty(propName)?.GetValue(src);
}

这是我的解决方案。它也适用于COM对象,并允许从COM对象访问集合/数组项。

public static object GetPropValue(this object obj, string name)
{
    foreach (string part in name.Split('.'))
    {
        if (obj == null) { return null; }

        Type type = obj.GetType();
        if (type.Name == "__ComObject")
        {
            if (part.Contains('['))
            {
                string partWithoundIndex = part;
                int index = ParseIndexFromPropertyName(ref partWithoundIndex);
                obj = Versioned.CallByName(obj, partWithoundIndex, CallType.Get, index);
            }
            else
            {
                obj = Versioned.CallByName(obj, part, CallType.Get);
            }
        }
        else
        {
            PropertyInfo info = type.GetProperty(part);
            if (info == null) { return null; }
            obj = info.GetValue(obj, null);
        }
    }
    return obj;
}

private static int ParseIndexFromPropertyName(ref string name)
{
    int index = -1;
    int s = name.IndexOf('[') + 1;
    int e = name.IndexOf(']');
    if (e < s)
    {
        throw new ArgumentException();
    }
    string tmp = name.Substring(s, e - s);
    index = Convert.ToInt32(tmp);
    name = name.Substring(0, s - 1);
    return index;
}
 public static object GetPropValue(object src, string propName)
 {
     return src.GetType().GetProperty(propName).GetValue(src, null);
 }

当然,您会想要添加验证和诸如此类的东西,但这就是它的要点。