Index-1 没有值

Question

我遇到了一个我完全不知道的最奇怪的错误。我将在此处发布描述以及一些代码，希望你们中的某个人能指出我正确的方向。

我的应用程序（Winforms）允许用户将项目添加到数据网格视图（绑定到列表），并且每次添加项目时，列表都会序列化为 xml 文件。最初启动应用程序时，程序会检查 xml 文件，如果找到，则将先前添加的项目添加到 dgv。

我还添加了一个 DataGridViewButtonColumn 来从 dgv（列表）中删除项目。这是一些代码。

主类：

 static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new formFoldingClient());
        }

表单的构造函数调用此方法来初始设置 dgv

private void InitialDataGridViewSetup()
        {
            dgvClients.DataSource = null;

            //adding delete button column
            DataGridViewButtonColumn btnDelete = new DataGridViewButtonColumn();
            btnDelete.Name = "btnDelete";
            btnDelete.Text = "Delete";
            btnDelete.HeaderText = "Delete";
            btnDelete.UseColumnTextForButtonValue = true;
            btnDelete.DefaultCellStyle.BackColor = Color.DarkBlue;
            btnDelete.DefaultCellStyle.ForeColor = Color.White;
            dgvClients.Columns.Add(btnDelete);

            RefreshDataGridView();
        }

每次添加或删除项目时，调用此方法刷新dgv：

 private void RefreshDataGridView()
            {
                dgvClients.DataSource = null;

                if (clientList.Count != 0)
                {
                    dgvClients.DataSource = clientList;
                    dgvClients.Show();
                    dgvClients.ClearSelection();


                }
            }

Method that gets triggered when Delete button on a row in the dgv is pressed, followed by the method the performs the delete

 private void dgvClients_CellClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == 0) //delete button has been clicked
            {
                DeleteClient(dgvClients.Rows[e.RowIndex].Cells[e.ColumnIndex + 1].FormattedValue.ToString());
            }
        }

        private void DeleteClient(string clientToDelete)
        {
            dgvGrid.DataSource = null;
            int removeAt = new int();

            for (int i=0; i<clientList.Count; i++)
            {
                if (clientList[i]._ClientName == clientToDelete)
                {
                    removeAt = i;
                    break;
                }
            }

            clientList.RemoveAt(removeAt);
            LogToFile("Removed client: " + clientToDelete);
            LogToBox("Removed client: " + clientToDelete);
            RefreshDataGridView();
            SaveConfigAsXml();
            LogToFile("Changes after deletion persisted to clients.xml.");

        }

我相信这是所有需要的代码。如果您还需要，请告诉我。

问题简介 当应用程序首次加载时，如果它找到 xml 并将这些项目加载到列表中，一切都会按预期执行。我可以添加更多项目，删除所有项目（一次一个）等。

但是，如果我在没有初始 xml 的情况下开始，添加项目不是问题。但是当我删除 dgv 中最后一个剩余的项目时，我在Main()的最后一行得到以下异常

Index out of range Exception: {"Index -1 does not have a value."}

堆栈跟踪

at System.Windows.Forms.CurrencyManager.get_Item(Int32 index)
   at System.Windows.Forms.CurrencyManager.get_Current()
   at System.Windows.Forms.DataGridView.DataGridViewDataConnection.OnRowEnter(DataGridViewCellEventArgs e)
   at System.Windows.Forms.DataGridView.OnRowEnter(DataGridViewCell& dataGridViewCell, Int32 columnIndex, Int32 rowIndex, Boolean canCreateNewRow, Boolean validationFailureOccurred)
   at System.Windows.Forms.DataGridView.SetCurrentCellAddressCore(Int32 columnIndex, Int32 rowIndex, Boolean setAnchorCellAddress, Boolean validateCurrentCell, Boolean throughMouseClick)
   at System.Windows.Forms.DataGridView.OnCellMouseDown(HitTestInfo hti, Boolean isShiftDown, Boolean isControlDown)
   at System.Windows.Forms.DataGridView.OnCellMouseDown(DataGridViewCellMouseEventArgs e)
   at System.Windows.Forms.DataGridView.OnMouseDown(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseDown(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.DataGridView.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at FoldingMonitorLocalClient.Program.Main() in C:\Users\xbonez\Documents\Visual Studio 2010\Projects\FoldingClient\FoldingClient\Program.cs:line 17
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

更多信息 所以，我刚刚意识到，如果我在 dgv 中有 n 项，则仅删除第一项也会导致相同的异常。删除项目 2 到 n 没问题。

读取 xml 并添加到列表的代码

 private void ReadFromConfigFile()
        {
            LogToFile("Beginning to read from clients.xml.");

            XmlSerializer deserializer = new XmlSerializer(typeof(List<Client>));

            try
            {
                List<Client> tempClientList = new List<Client>();
                using (Stream reader = new FileStream("clients.xml", FileMode.Open))
                {
                    tempClientList = ((List<Client>)deserializer.Deserialize(reader));
                }

                foreach (Client client in tempClientList)
                {
                    clientList.Add(client);
                }
            }
            catch (FileNotFoundException ex)
            {
                //config file does not exist
                this.LogToBox("No saved settings found.");
                this.LogToFile("No existing clients.xml present.", ex);
            }
            catch (Exception ex)
            {
                LogToBox("Unable to load saved settings. Please see log for more details.");
                LogToFile("Failed to read clients.xml.", ex);
            }
            finally
            {
                LogToFile("Finished reading clients.xml.");
            }
        }

点击添加按钮时的代码

private void btnAdd_Click(object sender, EventArgs e)
        {
            this.tbxClientName.BackColor = Color.White;
            this.tbxLogLoc.BackColor = Color.White;

            bool exists = false;

            foreach (Client client in clientList)
            {
                if (client._ClientName == this.tbxClientName.Text)
                    exists = true;
            }

            if (String.IsNullOrEmpty(tbxClientName.Text))
            {
                this.tbxClientName.BackColor = Color.Yellow;
                LogToBox("Enter Client Name");
                LogToFile("user attempted to add client without specifying client name.");
            }
            else if (String.IsNullOrEmpty(tbxLogLoc.Text))
            {
                this.tbxLogLoc.BackColor = Color.Yellow;
                LogToBox("Select WorkLog location.");
                LogToFile("User attempted to add client without specifying worklog location.");
            }
            else if (exists)
            {
                //client name entered by user already exists
                LogToBox("Client name " + this.tbxClientName.Text + " already exists. Enter another Client name.");
                LogToFile("Duplicate client name entered.");
                this.tbxClientName.BackColor = Color.Yellow;
            }
            else
            {
                //everything is valid. Add new client to list
                clientList.Add(new Client(tbxClientName.Text, tbxLogLoc.Text));
                LogToBox("Added new client: " + tbxClientName.Text + ".");
                LogToFile("Added new client: " + tbxClientName.Text + ".");

                this.tbxClientName.Text = String.Empty;
                this.tbxLogLoc.Text = String.Empty;

                RefreshDataGridView();
                SaveConfigAsXml();
            }            
        }

Answer 1

在运行 .NET 4.8.03752 的 Visual Studio 16.7.7 中将列表绑定到 DataGrid 时，此 Microsoft Winforms 错误（单击绑定到列表的 DataGrid 时崩溃）仍然存在。请注意，如果您指定绑定源，即使在使用 BindingList 时，下面的代码也会产生相同的错误：

var myProblems = new List<Problems>();
var bindingList = new BindingList<Problems>(myProblems);
var source = new BindingSource(bindingList, null);
myDataGrid.DataSource = source;

但是，如果我们不使用 BindingSource 并直接这样做，则不会出现该错误：

var myProblems = new BindingList<Problems>();
myDataGrid.DataSource = myProblems;

还要注意，如果您将 List 绑定到 DataGrid，则 Class 成员必须是 Properties（如 {get; set;} 而不是字段（如 int MyField;），因为 DataGrid 不会绑定到 Fields ，即使声明为 public。

Answer 2

这似乎是 .NET 中的某种内部绑定错误。 每当使用绑定到列表的 DataGridView 时，我都遇到了完全相同的异常。 我确实花了很多时间试图找到解决方案，今天我终于设法摆脱了这些异常 - 通过将 ICurrencyManagerProvider 接口添加到我的所有列表。 该接口只有一个“CurrencyManager”只读属性和一个“GetRelatedCurrencyManager”方法。 我只是在它们两个中都返回 Nothing 就是这样，不再有 CurrencyManager “索引 -1 没有价值”的东西。

编辑：好的，刚刚发现“正确的方法”实际上是使用 BindingList(of T) 类而不是 List(of T)

Answer 3

更新

修改 dgvClients_CellClick 方法以包含更多检查：

 if (e.ColumnIndex == 0) //delete button has been clicked
            {
                if (e.RowIndex >= 0)
                {
                    DataGridViewRow dataGridViewRow = dataGridView1.Rows[e.RowIndex];

                    if (dataGridViewRow.Cells.Count > 1)
                    {
                        DeleteClient(dataGridViewRow.Cells[e.ColumnIndex + 1].FormattedValue.ToString());
                    }
                }
                else
                {
                    LogToFile(e.RowIndex.ToString());
                }
            }

您可以修改dgvClients_CellClick 中的检查以包括e.RowIndex > 0，这应该可以防止异常。除此之外，要知道行为的确切原因，我们必须查看 add item 逻辑，并且可能也是 clientList。

您可能必须在手动添加项目后设置选定的行索引。