C# SharePoint复制列表项

我复制列表项时遇到问题。你看到错误了吗

当触发ExecuteQuery（）时，它会抛出一个异常，您可以在本文末尾看到

如果我注释掉foreach（），则没有例外

var spContext = SharePointContextProvider.Current.GetSharePointContext(ctx);
            using (var clientContext = spContext.CreateAppOnlyClientContextForSPHost())
            {
                var list = clientContext.Web.Lists.GetByTitle(listName);
                clientContext.Load(list, l => l.Fields);
                clientContext.ExecuteQuery();

                var sourceItem = list.GetItemById(sourceItemId);
                clientContext.Load(sourceItem);
                clientContext.ExecuteQuery();
                var sourceItemValues = sourceItem.FieldValues;

                var itemCreateInfo = new ListItemCreationInformation();
                var targetItem = list.AddItem(itemCreateInfo);

                foreach (var field in list.Fields)
                {
                    if (!field.ReadOnlyField && !field.InternalName.Equals("Attachments"))
                    {
                        object val = null;
                        sourceItemValues.TryGetValue(field.InternalName, out val);
                        targetItem[field.InternalName] = val;
                    }
                }

                targetItem.Update();
                clientContext.ExecuteQuery();

例外情况：

Microsoft.SharePoint.Client.ServerException: Invalid request.
   bei Microsoft.SharePoint.Client.ClientRequest.ProcessResponseStream(Stream responseStream)
   bei Microsoft.SharePoint.Client.ClientRequest.ProcessResponse()
   bei [...]
   bei lambda_method(Closure , ControllerBase , Object[] )
   bei System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   bei System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
   bei System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d()
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f()
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f()
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult)
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.<BeginInvokeAction>b__1c()
   bei System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult)

Microsoft.SharePoint.Client.ServerException:请求无效。
bei Microsoft.SharePoint.Client.ClientRequest.ProcessResponseStream（流响应流）
bei Microsoft.SharePoint.Client.ClientRequest.ProcessResponse（）
bei[…]
bei lambda_方法（闭包、控制器基、对象[]）
bei System.Web.Mvc.ReflectedActionDescriptor.Execute（ControllerContext ControllerContext，IDictionary`2参数）
bei System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod（ControllerContext ControllerContext，ActionDescriptor ActionDescriptor，IDictionary`2参数）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.b_u39（IAsyncResult asyncResult，ActionInvoke innerInvokeState）
bei System.Web.Mvc.Async.AsyncResultRapper.WrappedAsyncResult`2.CallEndDelegate（IAsyncResult asyncResult）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod（IAsyncResult asyncResult）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.b__3d（）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.c__DisplayClass46.b_u 3f（）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.c__DisplayClass46.b_u 3f（）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters（IAsyncResult asyncResult）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.c_uuDisplayClass21.c_uuDisplayClass2B.b_u1C（）
bei System.Web.Mvc.Async.AsyncControllerActionInvoker.c__DisplayClass21.b__1e（IAsyncResult asyncResult）

已解决 无法执行请求，因为不允许更改ContentType

此行（替换上面的行）解决了以下问题：

   if (!field.ReadOnlyField && !field.InternalName.Equals("Attachments") && !field.InternalName.Equals("ContentType"))

---

目标项目是什么？我只得到Id、DisplayName、FieldValue等属性。。。但不是。Item？

ListItem。Item

（根据）是用于通过内部名称访问字段值的属性。与我之前的评论相反，您可以使用括号表示法来访问它，比如

targetItem.Item[field.InternalName]=val