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在我们的Xamarin项目中使用Simple.OData.Client之前，我在LINQPad的帮助下进行了尝试。它的易用性给我留下了深刻的印象。当我将它构建到我们的Xamarin项目中时，我尝试从SharePoint的 REST Api 获取数据时遇到了异常。

Simple.OData.Client.WebRequestException：遇到意外的 WebException ---> System.Net.WebException：错误：SendFailure（写入标头时出错）---> System.Net.WebException：写入标头时出错 ---> System.IO。 IOException：身份验证或decr ... {Simple.OData.Client.WebRequestException：遇到意外的WebException ---> System.Net.WebException：错误：SendFailure（写入标头错误）---> System.Net.WebException：错误写入标头 ---> System.IO.IOException：身份验证或解密失败。---> Mono.Security.Protocol.Tls.TlsException：从服务器收到的证书无效。错误代码：0xffffffff800b010a

我相信，此异常是由于我们的SharePoint实例使用自签名证书这一事实引起的。我尝试通过将始终返回 true 到ServerCertificateValidationCallback来消除它

System.Net.ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, errors) => true;

现在我总是从 Simple.OData.Client 得到未经授权的异常

Simple.OData.Client.WebRequestException：未经授权

初始调用来自MainViewModel通过业务层

    private async void InitializeAsync()
    {
        // TODO [Anton Kalcik - Dienstag, 05. Mai 2015 17:09:55]: Show loading indicator
        TaskEntity getTaskForCurrentMonthAsyncTask = await _taksBusinessLayer.GetTaskForCurrentMonthAsync();
        _timeToDisplay = getTaskForCurrentMonthAsyncTask.DueDate - DateTime.Now;
        // TODO [Anton Kalcik - Dienstag, 05. Mai 2015 17:10:04]: Hide loading indicator

        StartCountdownTimer();
    }

执行调用的类是类SharePointTaskRepository

public class SharePointTaskRepository : ITaskRepository
{
    private readonly string _collectionName;
    private readonly ODataClient _oDataClient;

    public SharePointTaskRepository(Uri sharepointUri, string collectionName, ICredentials credentials)
    {
        if (sharepointUri == null)
        {
            throw new ArgumentNullException("sharepointUri");
        }
        if (String.IsNullOrWhiteSpace(collectionName))
        {
            throw new ArgumentException("Argument can't be null, empty or white space!", "collectionName");
        }
        if (credentials == null)
        {
            throw new ArgumentNullException("credentials");
        }

        _collectionName = collectionName;

        var oDataClientSettings = new ODataClientSettings(sharepointUri, credentials);
        _oDataClient = new ODataClient(oDataClientSettings);
    }

    public async Task<IEnumerable<TaskModel>> ReadAsync(Expression<Func<TaskModel, bool>> filter, Expression<Func<TaskModel, object>> orderBy, int numberOfResults)
    {
        return await _oDataClient
                    .For<TaskModel>(_collectionName)
                    .Filter(filter)
                    .OrderBy(orderBy)
                    .Top(numberOfResults)
                    .FindEntriesAsync();
    }
}

我仔细检查了凭据，这绝对是正确的。利用ServerCertificateValidationCallback的代码位于ApplicationRuntimeSettings中。此类是特定于平台的、单例的，并通过依赖注入作为所有其他对象提供。

[assembly: Dependency(typeof(ApplicationRuntimeSettings))]
namespace AZeitReminder.Droid.Infrastructure
{
    public class ApplicationRuntimeSettings : ApplicationRuntimeSettingsBase
    {
        public ApplicationRuntimeSettings()
        {
            System.Net.ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, errors) => true;
        }

        public override SQLiteConnection CreateSqLiteConnection()
        {
                string documentsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
                var path = Path.Combine(documentsPath, DatabaseFileName);
                var currentPlatform = new SQLitePlatformAndroid();
                var connection = new SQLiteConnection(currentPlatform, path);

                return connection;
        }

        public override CultureInfo GetCultureInfo()
        {
            var androidLocale = Java.Util.Locale.Default;
            var netLanguage = androidLocale.ToString().Replace("_", "-"); // NOTE [Anton Kalcik - Dienstag, 05. Mai 2015 17:21:10]: turns pt_BR into pt-BR
            return new CultureInfo(netLanguage);
        }
    }
}
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1 回答 1

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您可以尝试设置 PreAuthenticate = false; 为您的要求。Simple.ODataClient 在内部使用 HttpClientHandler。这个 HttpClientHandler 设置 PreAuthenticate = true; 但是您可以在 OnApplyClientHandler 中修改此处理程序并将该属性设置为 false。在你的代码中试试这个：

oDataClientSettings.OnApplyClientHandler = handler => handler.PreAuthenticate = false;

原因是您的 Sharepoint 服务器可以将“未授权”作为质询响应抛出，并且 WebRequest 不会回答质询，除非此属性为 false。

于 2015-05-06T11:37:32.290 回答