无法推断C＃中的类型，必须明确设置吗？

Question

这是我的代码：代码使用了第一个+第二个参数，当我添加第三个参数时它不再编译，我需要更改什么才能使它工作？

 /// <summary>
        /// Binds all dataObjects e.g. IPersonList, IDepartmentList, ITopicList... and creates a visual list of elements to display in the ElementTextBox
        /// </summary>
        /// <typeparam name="T">Type of dataObject in the dataObjects list</typeparam>
        /// <typeparam name="TProperty">value for the Type specified by the TResult paramter</typeparam>
        /// <param name="dataObjects">entity from database the user wants to show in the ElementTextBox</param>
        /// <param name="selectorDisplayMember">The property like FirstName that is shown as the elements text</param>
        /// <param name="selectorSortMember">The property like SortId that is used to pre-sort the dataObjects so the elements appear in the order before they were saved</param>
        public void BindElements<T, TProperty>(IEnumerable<T> dataObjects, Func<T, TProperty> selectorDisplayMember, Func<T, TProperty> selectorSortMember)
        { 
            if (dataObjects != null)
            {
                var sortedDataObjects = from d in dataObjects
                                        orderby selectorSortMember(d) ascending
                                        select d;

                Paragraph para = new Paragraph();

                foreach (T item in dataObjects)
                {
                    TProperty displayMemberValue = selectorDisplayMember(item);
                    InlineUIContainer uiContainer = ElementList.CreateElementContainer(displayMemberValue);
                    para.Inlines.Add(uiContainer);
                } 

                FlowDocument flowDoc = new FlowDocument(para);
                ElementList.Document = flowDoc;
            }            
        }

这工作： ElementUserControl.BindElements(customers, c => c.CustomerId);

但是当我添加第3个参数时：

ElementUserControl.BindElements(customers, c => c.CustomerId, c => c.SortId);

它不再起作用了？

Answer 1

问题在于你引入的歧义，因为第二个和第三个参数都可以推断TProperty 。 您可能想尝试引入第三个泛型类型参数，以便您拥有TDisplayProperty于您的用例的TDisplayProperty和TSortProperty 。