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[Problem Description]
When you move focus from a new DataSource row to an existing one in DataGridView on a Windows Form Application program, the captioned error occurs. You set to DataSource of DataGridView a component like BindingSource that supports cursor move by CurrencyManager. When you use the MoveFirst method of BindingSource to move from a new row to an existing one and then go back to the new one, the error occurs. When you use an ARROW key to move from a new row to an existing one, the symptom does not occur. No error occurs either when you call the Validate method of the form before calling MoveFirst.

I hope the error does not occur even if the Validate method is not called. This is because, at present, a program that handles BindingSource needs to consider if BindingSource is bound to DataGridView, which results in high coupling.

When you step in .NET Framework source code and use an ARROW key to move from a new row to an existing one, CancelEdit and CancelNew occur. On the other hand, when the MoveFirst method is called, EndEdit and EndNew occur. When you use the DOWN ARROW key to move next, CancelEdit and CancelNew occur. Like this, inconsistency is generated in the status inside DataGridView.

To prevent this, CurrencyManager or BindingSource should be extended to add a new event like "PositionChanging" or "CurrentChanging" that occurs before position change, and DataGridView should catch this event to raise CancelEdit and CancelNew.

[Repro Steps]
1) Create a Windows Form Application program.
2) Place DataGridView, BindingSource, and ToolStrip.
3) Add a button on the ToolStrip.
4) Write source code on the form as below. (The Load event of the form and the Click event of the button should be caught.)

using System;
using System.ComponentModel;
using System.Windows.Forms;

namespace DataGridViewBug
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

public class CodeAndName
{
public int? Code { get; set; }
public string Name { get; set; }
}

private void Form1_Load(object sender, EventArgs e)
{
dataGridView1.AutoGenerateColumns = true;
bindingSource1.DataSource = new BindingList<CodeAndName>();
}

private void toolStripButton1_Click(object sender, EventArgs e)
{
//Validate();
bindingSource1.MoveFirst();
}
}
}

5) Build and run.
6) Add data in the first row.
7) Move to the second row.
8) Click the button on the ToolStrip and move to the first row.
9) Use the DOWN ARROW key to move to the second row.

[Actual Results]
The captioned error occurs.

[Expected Results]
No error occurs.

Thanks for your feedback. We are routing this bug to the product unit who works on that specific feature area. The team will review this issue and make a decision on whether they will fix it or not for the next release.

Thank you,
Visual Studio Product Team

Thanks for your feedback on the .NET Framework!

We are able to reproduce the bug that you reported and plan to conduct in-depth investigation. Since team here is focusing on stablizing and finalizing VS2010 RC bits, we'll keep you updated once progress is made on this problem.

Regards,
UIFx Team

（こちらは、[投稿者: Microsoft、投稿日時: 2009/11/11 4:56] の和訳です。）

フィードバックをお寄せいただき、ありがとうございます。 こちらのバグに関しましては、該当する機能を専門で担当している製品チームに報告させていただきます。 今後は、同チームが問題を再調査し、次期リリース版での修正について判断する予定です。 よろしくお願いいたします。

Visual Studio 製品チーム

（こちらは、[投稿者: Microsoft、投稿日時: 2009/11/11 18:00] の和訳です。）

.NET Framework に関するフィードバックをお寄せいただき、ありがとうございます！

私たちの方で 三輪の牛 さんからご報告いただきましたバグを再現することができましたので、掘り下げた調査を実施したいと考えております。 担当チームは現在、Visual Studio 2010 RC 版の安定性確認および最終仕上げに集中しておりますので、こちらの問題に関しましては、進捗があり次第お知らせさせていただきます。 よろしくお願いいたします。

UIFx チーム