c# - 从绑定(bind)到 DataGridView 的 DataTable 中删除最后一个 DataRow 时如何防止出错？

Question

在我的 WinForms 应用程序中，按下按钮会触发以下逻辑:

    private void ExecuteSelectedConsoleCommand()
    {
        var commandsRow = GetCommandsRow();
        var consoleCommand = GetConsoleCommand(commandsRow);
        Task.Factory.StartNew(() =>
        {
            var runningCommandRow =
                  runtimeDataSet.RunningCommands.AddRunningCommandsRow(Guid.NewGuid(),
                  consoleCommand.OneLineDescription);

            consoleCommand.Run(null);

            runningCommandRow.Delete();
        });
    }

BindingSource 用于让 DataGridView 自动更新自身。

截至目前，如果没有以下 hack，我会收到一条错误消息，指出“索引 0 无效”。

        // prevents error when removing last row from data bound datagridview
        var placeholder = runtimeDataSet
                             .RunningCommands
                             .AddRunningCommandsRow(Guid.NewGuid(), "PLACEHOLDER");

使用上面的代码，它会导致 DataGridView 中始终至少有一行，它工作正常。

我该如何解决这个问题？

注意:这似乎是很多其他人会遇到的事情，但我的网络搜索失败了..

Answer 1

我遇到了同样的问题。经过一些尝试和错误后，我发现您必须处理 datagridview 的几个事件才能使它消失，甚至需要忽略一些错误。我不记得我做了什么来规避这个错误，但我认为以下片段可能会提供一些见解(评论中的解释):

删除行:

//When I remove a row that has been added, but not commited return from the function
//run the update function only if the row is commited (databound)
private void dgvTest_RowsRemoved(object sender, DataGridViewRowsRemovedEventArgs e) {
    if (_lastDataRow == null || _lastDataRow.RowState == DataRowState.Added)
        return;
    UpdateRowToDatabase();
}

行验证:

//I got the kind of Index not valid or other index errors
//RowValidating is fired when entering the row and when leaving it
//In my case there was no point in validating on row enter
private void dgvTest_RowValidating(object sender, DataGridViewCellCancelEventArgs e)    {
if (Disposing)
     return;
if (!dgvTest.IsCurrentRowDirty) {
     return;
    }
try {
var v = dgvTest.Rows[e.RowIndex].DataBoundItem;
} catch {
return;
}
}

数据错误:

//I had to trap some errors and change things accordingly
private void dgvTest_DataError(object sender, DataGridViewDataErrorEventArgs e) {
        if (e.Exception.Message.Contains("Index") && e.Exception.Message.Contains("does not have a value")) {
            //when editing a new row, after first one it throws an error
            //cancel everything and reset to allow the user to make the desired changes
            bindingSource.CancelEdit();
            bindingSource.EndEdit();
            bindingSource.AllowNew = false;
            bindingSource.AllowNew = true;
            e.Cancel = true;
            dgvTest.Visible = false;
            dgvTest.Visible = true;
        }
    }

行输入:

 //Some problemes occured when entering a new row
 //This resets the bindingsource's AllowNew property so the user may input new data
 private void dgvTest_RowEnter(object sender, DataGridViewCellEventArgs e) {
            if (!_loaded)
                return;
            if (e.RowIndex == dgvTest.NewRowIndex)
                if (String.IsNullOrWhiteSpace(dgvTest.Rows[e.RowIndex == 0 ? e.RowIndex : e.RowIndex - 1].Cells[_idColumn].Value.ToStringSafe())) {
                    bindingSource.CancelEdit();
                    bindingSource.AllowNew = false;
                    bindingSource.AllowNew = true;
                }
        }

希望这对您有所帮助!