泛型C＃ - 从静态泛型类创建实例

Question

I have a factory class in my application but due to my lack of knowledge around generics I am not sure how to go about creating an instance of this particular type.

Would someone be kind enough to point me how to call this class so that it returns a service... Any help would be kindly appreciated.

public class ServiceFactory<TService> where TService : WebServicesClientProtocol, new()
{

    public static TService GetSecureService(string serviceUrl, X509Certificate certificate)
    {
        if (serviceUrl == null)
        {
            throw new ArgumentNullException(nameof(serviceUrl), "Service URL must be specified.");
        }

        if (serviceUrl == string.Empty)
        {
            throw new ArgumentException("Service URL cannot be empty.", nameof(serviceUrl));
        }

        if (certificate == null)
        {
            throw new ArgumentNullException(nameof(certificate), "Client certificate must be specified.");
        }

        return Service(serviceUrl, certificate);
    }

    private static TService Service(string serviceUrl, X509Certificate certificate)
    {
        return ConfigureService((TService)Activator.CreateInstance(typeof(TService)), serviceUrl, certificate);
    }

    public static TService ConfigureService(TService service, string serviceUrl, X509Certificate certificate)
    {
        service.PreAuthenticate = true;
        service.Credentials = CredentialCache.DefaultCredentials;
        service.Timeout = 250;
        service.Url = serviceUrl;

        return ConfigureRequestSignature(service, certificate);
    }

    private static TService ConfigureRequestSignature(TService service, X509Certificate certificate)
    {
        X509SecurityToken signatureToken = new X509SecurityToken(certificate);
        MessageSignature signature = new MessageSignature(signatureToken);

        signature.SignatureOptions = SignatureOptions.IncludeTimestamp | SignatureOptions.IncludeSoapBody | SignatureOptions.IncludeMessageId | SignatureOptions.IncludeAction;

        SoapContext requestContext = service.RequestSoapContext;
        requestContext.Security.Tokens.Add(signatureToken);
        requestContext.Security.Elements.Add(signature);

        // TTL must be less than 60 seconds, otherwise the request will be discarded.
        requestContext.Security.Timestamp.TtlInSeconds = 50;

        return service;
    }
}

Answer 1

在不知道可以实例化的类的名称的情况下......

var service = ServiceFactory<ConcreteImplementationService>.GetSecureService(url, cert);

Answer 2

Since you're using static methods, use method level generic parameters:

TService GetSecureService<TService>(string serviceUrl, X509Certificate certificate)
   where TService : WebServicesClientProtocol, new()
{
...
     return Service<TService>(serviceUrl, certificate);
}

You will probably find all the methods will use this pattern and pass the generic type down as I did when calling Service() above.

MSDN Article for generic methods: https://msdn.microsoft.com/en-us/library/twcad0zb.aspx