c# - 是否可以在 C# 中使用运行时生成的字段名称访问对象的字段

Question

这就是我的意思：

我需要能够替换这个丑陋的 C# 代码：

if (attribute.Name == "Name") machinePool.Name = attribute.Value;
else if (attribute.Name == "Capabilities") machinePool.Capabilities = attribute.Value;
else if (attribute.Name == "FillFactor") machinePool.FillFactor = attribute.Value;

变成这样的东西：

machinePool.ConvertStringToObjectField(attribute.Name) = attribute.Value;

没有 ConvertStringToObjectField() 方法，但如果可能的话，我想要这样的东西。我可以访问 machinePool 对象类代码，因此我可以添加必要的代码，但我不确定它可能是什么代码，甚至是否可以在 C# 中执行。

Answer 1

是的，您可以通过反射来做到这一点：

var fieldInfo = machinePool.GetType().GetField(attribute.Name);
fieldInfo.SetValue(machinePool, attribute.Value);

您还可以创建一个扩展方法来使事情变得更容易：

public static void SetField(this object o, string fieldName, object value)
{
    var fi = o.GetType().GetField(fieldName);
    fi.SetValue(o, value);
}

Answer 2

是的你可以。这是我想将属性名称作为字符串获取（即处理 PropertyChangedEventHandler）但我不想使用字符串本身时使用的一些代码：

    public static string GetPropertyName<T>(Expression<Func<T, object>> propertyExpression)
    {
        Check.RequireNotNull<object>(propertyExpression, "propertyExpression");
        switch (propertyExpression.Body.NodeType)
        {
            case ExpressionType.MemberAccess:
                return (propertyExpression.Body as MemberExpression).Member.Name;
            case ExpressionType.Convert:
                return ((propertyExpression.Body as UnaryExpression).Operand as MemberExpression).Member.Name;
        }
        var msg = string.Format("Expression NodeType: '{0}' does not refer to a property and is therefore not supported", 
            propertyExpression.Body.NodeType);
        Check.Require(false, msg);
        throw new InvalidOperationException(msg);
    }

这里有一些测试代码可以帮助您完成它：

[TestFixture]
public class ExpressionsExTests
{
    class NumbNut
    {
        public const string Name = "blah";
        public static bool Surname { get { return false; } }
        public string Lame;
        public readonly List<object> SerendipityCollection = new List<object>();
        public static int Age { get { return 12; }}
        public static bool IsMammel { get { return _isMammal; } }
        private const bool _isMammal = true;
        internal static string BiteMe() { return "bitten"; }
    }

    [Test]
    public void NodeTypeIs_Convert_aka_UnaryExpression_Ok()
    {
        Assert.That(ExpressionsEx.GetPropertyName<NumbNut>(nn => NumbNut.Age), Is.EqualTo("Age"));
        Assert.That(ExpressionsEx.GetPropertyName<NumbNut>(nn => NumbNut.IsMammel), Is.EqualTo("IsMammel"));
        Assert.That(ExpressionsEx.GetPropertyName<NumbNut>(nn => NumbNut.Surname), Is.EqualTo("Surname"));
    }

    [Test]
    public void NodeTypeIs_MemberAccess_aka_MemberExpression_Ok()
    {
        Assert.That(ExpressionsEx.GetPropertyName<NumbNut>(nn => nn.SerendipityCollection), Is.EqualTo("SerendipityCollection"));
        Assert.That(ExpressionsEx.GetPropertyName<NumbNut>(nn => nn.Lame), Is.EqualTo("Lame"));
    }

    [Test]
    public void NodeTypeIs_Call_Error()
    {
        CommonAssertions.PreconditionCheck(() => ExpressionsEx.GetPropertyName<NumbNut>(nn => NumbNut.BiteMe()),
                                           "does not refer to a property and is therefore not supported");
    }

    [Test]
    public void NodeTypeIs_Constant_Error() {
        CommonAssertions.PreconditionCheck(() => ExpressionsEx.GetPropertyName<NumbNut>(nn => NumbNut.Name),
                                           "does not refer to a property and is therefore not supported");
    }

    [Test]
    public void IfExpressionIsNull_Error()
    {
        CommonAssertions.NotNullRequired(() => ExpressionsEx.GetPropertyName<NumbNut>(null));
    }

    [Test]
    public void WasPropertyChanged_IfPassedNameIsSameAsNameOfPassedExpressionMember_True()
    {
        Assert.That(ExpressionsEx.WasPropertyChanged<NumbNut>("SerendipityCollection", nn => nn.SerendipityCollection), Is.True);
    }

    [Test]
    public void WasPropertyChanged_IfPassedPropertyChangeArgNameIsSameAsNameOfPassedExpressionMember_True()
    {
        var args = new PropertyChangedEventArgs("SerendipityCollection");
        Assert.That(ExpressionsEx.WasPropertyChanged<NumbNut>(args, nn => nn.SerendipityCollection), Is.True);
    }

}

高温高压

绿柱石

Answer 3

您可以执行以下操作：

void SetPropertyToValue(string propertyName, object value)
{
    Type type = this.GetType();
    type.GetProperty(propertyName).SetValue(this, value, null);
}

Then use it like:

machinePool.SetPropertyToValue(attribute.Name, attribute.Value);