使用 HttpClient 呼叫 WebService
.NET 在 WebService 有提供完整的支援，通常只需要使用 Visual Studio 加入「Web 參考」就能完成呼叫。然後，有時因為某些因素，如開發環境無法連接到 WebService，因此無法加入參考，此時可能會嘗試在不加入 Web 參考的情況下呼叫 WebService。
.NET Framework 中常見的作法是使用 WebClient 和 Reflection 的組合來動態產生 WebService 服務的程式碼，程式碼如下：
csharp
public class InvokeWebService {
public object InvokeWebservice(string url, string @namespace, string classname, string methodname, object[] args) {
try {
if ((classname == null) || (classname == "")) {
classname = GetWsClassName(url);
}
System.Net.WebClient wc = new System.Net.WebClient();
System.IO.Stream stream = wc.OpenRead(url + "?WSDL");
System.Web.Services.Description.ServiceDescription sd = System.Web.Services.Description.ServiceDescription.Read(stream);
System.Web.Services.Description.ServiceDescriptionImporter sdi = new System.Web.Services.Description.ServiceDescriptionImporter();
sdi.AddServiceDescription(sd, "", "");
System.CodeDom.CodeNamespace cn = new System.CodeDom.CodeNamespace(@namespace);
System.CodeDom.CodeCompileUnit ccu = new System.CodeDom.CodeCompileUnit();
ccu.Namespaces.Add(cn);
sdi.Import(cn, ccu);
Microsoft.CSharp.CSharpCodeProvider csc = new Microsoft.CSharp.CSharpCodeProvider();
System.CodeDom.Compiler.ICodeCompiler icc = csc.CreateCompiler();
System.CodeDom.Compiler.CompilerParameters cplist = new System.CodeDom.Compiler.CompilerParameters();
cplist.GenerateExecutable = false;
cplist.GenerateInMemory = true;
cplist.ReferencedAssemblies.Add("System.dll");
cplist.ReferencedAssemblies.Add("System.XML.dll");
cplist.ReferencedAssemblies.Add("System.Web.Services.dll");
cplist.ReferencedAssemblies.Add("System.Data.dll");
System.CodeDom.Compiler.CompilerResults cr = icc.CompileAssemblyFromDom(cplist, ccu);
if (true == cr.Errors.HasErrors) {
System.Text.StringBuilder sb = new StringBuilder();
foreach (System.CodeDom.Compiler.CompilerError ce in cr.Errors) {
sb.Append(ce.ToString());
sb.Append(System.Environment.NewLine);
}
throw new Exception(sb.ToString());
}
System.Reflection.Assembly assembly = cr.CompiledAssembly;
Type t = assembly.GetType(@namespace + "." + classname, true, true);
object obj = Activator.CreateInstance(t);
System.Reflection.MethodInfo mi = t.GetMethod(methodname);
return mi.Invoke(obj, args);
} catch (Exception ex) {
throw new Exception(ex.InnerException.Message, new Exception(ex.InnerException.StackTrace));
}
}
private string GetWsClassName(string wsUrl) {
string[] parts = wsUrl.Split('/');
string[] pps = parts[parts.Length - 1].Split('.');
return pps[0];
}
}但是在 .NET Core 之後，因為沒有「System.Web.Services」這個相關的 Library，所以我參考了這篇文章「.Net core 调用WebService」，使用 HttpClient 以 SOAP 訊息格式來呼叫 WebService。
有關 WebService SOAP 訊息格式內容，可以找一個 C# 寫的 WebService，在網址「{httpUrl}?op={method}」查看此 Method 的 Request 和 Response 格式，一般會有提供「SOAP 1.1」、「SOAP 1.2」和「HTTP POST」三種格式，以下是本次使用的「SOAP 1.2」格式範例。
放大顯示。
當然，我對文章中的解法並不太滿意，因為實際輸入和輸出的型別不一定是簡單型別，所以我使用 XmlSerializer 來進行 Object 與 XML 相互轉換，最終的程式碼如下：
csharp
public static class WebServiceUtils {
private static readonly HttpClient httpClient = new HttpClient();
public static async Task<TResponse> ExecuteAsync<TResponse>(string uri, string method, IDictionary<string, string> arguments, string @namespace = "http://tempuri.org/") {
XmlSerializerNamespaces serializerNamespaces = new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty });
XmlWriterSettings settings = new XmlWriterSettings {
Indent = true,
OmitXmlDeclaration = true
};
string argsXml = string.Join("", arguments.Select(x => {
Type type = x.Value.GetType();
XmlSerializer _serializer = new XmlSerializer(type);
StringBuilder sb = new StringBuilder();
using (XmlWriter writer = XmlWriter.Create(sb, settings)) {
_serializer.Serialize(writer, x.Value, serializerNamespaces);
// 原本 Serializer 後，Root 會是 Type Name，所以要替換成 Dictionary Key
// 至於正規式不用 Type Name 達到比較精準替換原因為遇到別名的會有問題
// 例如：Int32 會變成 <int></int> 而非 <Int32></Int32>
return Regex.Replace(sb.ToString(), $@"((?<=^<)(\w*)(?=>))|(?<=</)\w*(?=>$)", x.Key);
}
}));
string soapXml = $@"
<soap12:Envelope xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"" xmlns:xsd=""http://www.w3.org/2001/XMLSchema"" xmlns:soap12=""http://www.w3.org/2003/05/soap-envelope"">
<soap12:Body>
<{method} xmlns=""{@namespace}"">
{argsXml}
</{method}>
</soap12:Body>
</soap12:Envelope>
";
StringContent content = new StringContent(soapXml, Encoding.UTF8, "text/xml");
using (HttpResponseMessage message = await httpClient.PostAsync(uri, content).ConfigureAwait(false)) {
if (!message.IsSuccessStatusCode) {
throw new HttpRequestException($"HTTP request failed with status code {message.StatusCode}: {message.ReasonPhrase}");
}
string result = await message.Content.ReadAsStringAsync().ConfigureAwait(false);
XDocument xdoc = XDocument.Parse(result);
XNamespace ns = @namespace;
string resultTag = method + "Result";
XElement xelement = xdoc.Descendants(ns + resultTag).Single();
XmlSerializer serializer = new XmlSerializer(typeof(TResponse), new XmlRootAttribute(resultTag) { Namespace = @namespace });
using (XmlReader reader = xelement.CreateReader()) {
return (TResponse)serializer.Deserialize(reader);
}
}
}
}實際測試
這邊先定義巢狀的 Request 和 Response 來作為 WebService 的參數和回傳值，嘗試看是否能支援較複雜的型別。
csharp
public class Request {
public int Id { get; set; }
public string Name { get; set; }
public List<string> Strings { get; set; }
public List<InnerRequest> InnerRequests { get; set; }
}
public class InnerRequest {
public int Id { get; set; }
public string Name { get; set; }
}
public class Response {
public int Id { get; set; }
public string Name { get; set; }
public List<string> Strings { get; set; }
public List<InnerResponse> InnerResponse { get; set; }
}
public class InnerResponse {
public int Id { get; set; }
public string Name { get; set; }
}WebService 刻意使用多個參數。
csharp
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
// 若要允許使用 ASP.NET AJAX 從指令碼呼叫此 Web 服務，請取消註解下列一行。
// [System.Web.Script.Services.ScriptService]
public class TestWebService : System.Web.Services.WebService {
[WebMethod]
public Response HelloWorld(Request request1, Request request2) {
return new Response {
Id = 31,
Name = "32",
Strings = new List<string> {
"331",
"332"
},
InnerResponse = new List<InnerResponse> {
new InnerResponse { Id = 3411, Name = "3412" },
new InnerResponse { Id = 3421, Name = "3422" }
}
};
}
}csharp
string uri = "https://localhost:44399/TestWebService.asmx";
string method = "HelloWorld";
IDictionary<string, object> arguments = new Dictionary<string, object>();
Request request1 = new Request {
Id = 11,
Name = "12",
Strings = new List<string> {
"131",
"132"
},
InnerRequests = new List<InnerRequest> {
new InnerRequest { Id = 1411, Name = "1412" },
new InnerRequest { Id = 1421, Name = "1422" }
}
};
Request request2 = new Request {
Id = 21,
Name = "22",
Strings = new List<string> {
"231",
"232"
},
InnerRequests = new List<InnerRequest> {
new InnerRequest { Id = 2411, Name = "2412" },
new InnerRequest { Id = 2421, Name = "2422" }
}
};
arguments.Add("request1", request1);
arguments.Add("request2", request2);
Response response = await WebServiceUtils.ExecuteAsync<Response>(uri, method, arguments);從監看式看 WebService 有正確接收參數。
從監看式看執行結果和 WebService 回傳的一致。
異動歷程
- 2023-02-13 初版文件建立。