Linq to SQL - 无法更新

I'm having some troubles with updating linq to sql entities. For some reason, I can update every single field of my item entity besides name.

这是我写的两个简单的测试:

Here are two simple tests I wrote:

 [TestMethod]
        public void TestUpdateName( ) {
            using ( var context = new SimoneDataContext( ) ) {
                Item item = context.Items.First( );

                if ( item != null ) {
                    item.Name = "My New Name";
                    context.SubmitChanges( );
                }
            }
        }

        [TestMethod]
        public void TestUpdateMPN( ) {
            using ( var context = new SimoneDataContext( ) ) {
                Item item = context.Items.First( );

                if ( item != null ) {
                    item.MPN = "My New MPN";
                    context.SubmitChanges( );
                }
            }
        }

不幸的是，TestUpdateName() 失败并出现以下错误:System.Data.SqlClient.SqlException: 关键字WHERE"附近的语法不正确..

Unfortunately, TestUpdateName() fails with the following error: System.Data.SqlClient.SqlException: Incorrect syntax near the keyword 'WHERE'..

这是输出的 SQL:

UPDATE [dbo].[Items] SET WHERE ([Id]= @p0) AND ([CategoryId] = @p1) AND ([MPN] = @p2) AND ([Height] = @p3) AND([宽度] = @p4) AND ([重量] = @p5)AND ([长度] = @p6) AND([管理成本] = @p7)-- @p0: 输入整数 (大小 = 0; Prec = 0; 比例 = 0) [1]-- @p1: Input Int (Size = 0; Prec = 0; Scale = 0) [1]-- @p2: 输入 VarChar (Size = 10; Prec = 0; Scale = 0) [我的新 MPN]-- @p3:输入十进制(大小 = 0；Prec = 5；比例 = 3)[30.000]-- @p4:输入十进制(大小 = 0；Prec = 5；比例 = 3)[10.000]-- @p5:输入十进制(大小 = 0；Prec = 5；比例 = 3)[40.000]-- @p6:输入十进制(大小 = 0；Prec = 5；比例 = 3)[30.000]-- @p7:输入货币(大小 = 0；Prec = 19；比例 = 4)[350.0000]-- 上下文:SqlProvider(Sql2008) 模型:AttributedMetaModel 构建:3.5.30729.4926

UPDATE [dbo].[Items] SET WHERE ([Id] = @p0) AND ([CategoryId] = @p1) AND ([MPN] = @p2) AND ([Height] = @p3) AND ([Width] = @p4) AND ([Weight] = @p5) AND ([Length] = @p6) AND ([AdministrativeCost] = @p7) -- @p0: Input Int (Size = 0; Prec = 0; Scale = 0) [1] -- @p1: Input Int (Size = 0; Prec = 0; Scale = 0) [1] -- @p2: Input VarChar (Size = 10; Prec = 0; Scale = 0) [My New MPN] -- @p3: Input Decimal (Size = 0; Prec = 5; Scale = 3) [30.000] -- @p4: Input Decimal (Size = 0; Prec = 5; Scale = 3) [10.000] -- @p5: Input Decimal (Size = 0; Prec = 5; Scale = 3) [40.000] -- @p6: Input Decimal (Size = 0; Prec = 5; Scale = 3) [30.000] -- @p7: Input Money (Size = 0; Prec = 19; Scale = 4) [350.0000] -- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 3.5.30729.4926

如您所见，没有生成更新(SET 为空...)我不知道为什么会这样.

As you can see, no update is being generated (SET is empty ...) I have no clue why is this happening.

并且已经提前......是的，表Item有一个PK(Id).谢谢提前！

And already in advance ... YES, the table Item has a PK (Id). Thank you in advance!

更新:该错误似乎是由覆盖 GetHashcode() 引起的.这是我目前的实现:

Update: It appears that the error is caused by overriding GetHashcode(). This is my current implementation: