表达式<Func>问题

Question

我希望能够清楚简明地解释这一点.我有一个表达方式:

Expression<Func<TObject, TProperty>> expression

我正试图从中获取属性名称.一切都很好和花花公子'UNTIL',遇到一个转换表达式(在GetPropertyName方法 - 这是我想要排序问题的地方),即正常的属性可能会出来,{e =>e.EmployeeID}但在少数情况下,我得到的结果{e => Convert(e.EmployeeID)}.这实际上意味着我无法识别正确的属性名称(我不想解析诸如Convert()等的异常).

如何将表达式名称干净地提取为属性.下面是我正在使用的代码,所以请随意篡改:

public static class ExpressionExtensions
{
    public static string GetPropertyName<TObject, TProperty>(
        this Expression<Func<TObject, TProperty>> expression) where TObject : class
    {
        if (expression.Body.NodeType == ExpressionType.Call)
        {
            MethodCallExpression methodCallExpression = (MethodCallExpression)expression.Body;
            string name = ExpressionExtensions.GetPropertyName(methodCallExpression);
            return name.Substring(expression.Parameters[0].Name.Length + 1);
        }
        return expression.Body.ToString().Substring(expression.Parameters[0].Name.Length + 1);
    }

    private static string GetPropertyName(MethodCallExpression expression)
    {
        MethodCallExpression methodCallExpression = expression.Object as MethodCallExpression;
        if (methodCallExpression != null)
        {
            return GetPropertyName(methodCallExpression);
        }
        return expression.Object.ToString();
    }
}

而我正如此调用它:

string propertyName = expression.GetPropertyName();
// which ideally should return a value of EmployeeID or ReportsTo
// as per the usage example below

这会影响一些仲裁用法,例如:

var tree = items2.AsHierarchy(e => e.EmployeeID, e => e.ReportsTo);

希望这能提供足够的信息让我脱离套索!!

干杯

Answer 1

您应该在表达式树中有一个"转换"节点,因此您应该测试nodetype为"convert"的节点,然后如果为true,则在转换为字符串之前更深一级.尝试这样的事情:

        public static string GetMemberName<TSource,TMember>(this Expression<Func<TSource,TMember>> memberReference)
    {
        MemberExpression expression = memberReference.Body as MemberExpression;
        if (expression == null)
        {
            UnaryExpression convertexp = memberReference.Body as UnaryExpression;
            if(convertexp!=null)
            expression = convertexp.Operand as MemberExpression; ;
        }
        if(expression==null)
            throw new ArgumentNullException("memberReference");

        return expression.Member.Name;
    }