不允许在谷歌电子表格中重复

我使用谷歌电子表格一样的数据库表,希望第一个字段是唯一的。如何在更新前检查字段唯一性。或者我可以设置列A不允许不唯一的字段?

我正在使用C#处理电子表格:

   private void button3_Click(object sender, EventArgs e)
    {
        string spreadsheetId = "1IAD2okAWZD7anbt5L4ybgD2dxHBGmsY6IkNIWHBQkBM";
        string ApplicationName = "sheets";
        UserCredential credential;

        using (var stream = new FileStream("credentials_1.json", FileMode.Open, FileAccess.Read))
        {
            string credPath = "token.json";
            credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                GoogleClientSecrets.Load(stream).Secrets,
                Scopes,
                "user",
                CancellationToken.None,
                new FileDataStore(credPath, true)).Result;
            Console.WriteLine("Credential file saved to: " + credPath);
        }

        // Create Google Sheets API service.
        var service = new SheetsService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = ApplicationName,
        });




        String range = "new first sheet!A1"; // mano
        //var range = "{sheet}!D543";
        var valueRange = new ValueRange();

        var oblist = new List<object>() { "aaa","bbb","ccc" };
        valueRange.Values = new List<IList<object>> { oblist };

        var updateRequest = service.Spreadsheets.Values.Append(valueRange, spreadsheetId, range);

        updateRequest.ValueInputOption = SpreadsheetsResource.ValuesResource.AppendRequest.ValueInputOptionEnum.USERENTERED;
        var appendReponse = updateRequest.Execute();

    }