private void textBoxProjectName_TextChanged(object sender, System.EventArgs e)
{
	ValidateProjectName();
}

private bool ValidateProjectName()
{
	if(this.textBoxProjectName.Text == "")
	{
		//エラー表示
		this.errorProvider.SetError(this.textBoxProjectName, "Please input project name.");
		this.buttonOk.Enabled = false;
		return false;
	}

	if(Directory.Exists(this.textBoxProjectName.Text))
	{
		//エラー表示
		this.errorProvider.SetError(this.textBoxProjectName, "The project name already exists.");
		this.buttonOk.Enabled = false;
		return false;
	}

	//エラー取り消し
	this.errorProvider.SetError(this.textBoxProjectName, null);
	this.buttonOk.Enabled = true;
	return true;
}