c# - 将表达式> 转换为表达式>

Question

我有以下 C# 代码，它从 lambda 表达式获取成员名称:

public static class ObjectInformation<T>
{
    public static string GetPropertyName<TProp>(Expression<Func<T, TProp>> propertyLambda)
    {
        var memberExpression = propertyLambda.Body as MemberExpression;
        if (memberExpression == null)
        {
            throw new ArgumentException("Lambda must return a property.");
        }

        return memberExpression.Member.Name;
    }
}

public static class ObjectInformation
{
   public static string GetPropertyName<T>(Expression<Func<T>> propertyLambda)
    {
        var memberExpression = propertyLambda.Body as MemberExpression;
        if (memberExpression == null)
        {
            throw new ArgumentException("Lambda must return a property.");    
        }

        return memberExpression.Member.Name;
    }
}

我这样调用方法:

ObjectInformation<RemoteCollectionContentViewModel>.GetPropertyName(e => e.SomeProperty);
ObjectInformation.GetPropertyName(() => SomeProperty)

我希望第二种方法使用第一种方法(不重复代码)，所以我需要转换 Func<T>至 Func<T, TProp> .我怎样才能做到这一点？

Answer 1

没有简单的方法来转换表达式类型。您必须重建整个表达式树。这不值得麻烦。有一种提取通用逻辑的好方法:

public static class ObjectInformation
{
    public static string GetPropertyName<T, TProp> (Expression<Func<T, TProp>> propertyLambda)
    {
        return GetPropertyName((LambdaExpression)propertyLambda);
    }

    public static string GetPropertyName<T> (Expression<Func<T>> propertyLambda)
    {
        return GetPropertyName((LambdaExpression)propertyLambda);
    }

    private static string GetPropertyName (LambdaExpression propertyLambda)
    {
        var memberExpression = propertyLambda.Body as MemberExpression;
        if (memberExpression == null)
            throw new ArgumentException("Lambda must return a property.");
        return memberExpression.Member.Name;
    }
}