将Expression<Func<T1>>转换为Expression<Func<T1，T2>>

Question

我有以下C#代码，它从lambda表达式中获取成员名：

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;
    }
}

我称之为这样的方法：

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

我希望第二个方法使用第一个方法(而不是复制代码)，所以我需要将Func<T>转换为Func<T, TProp>。我怎样才能做到这一点？

Answer 1

转换表达式类型没有简单的方法。你必须重建整个表达式树。这是不值得的麻烦。有一种很好的提取共同逻辑的老方法：

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;
    }
}