C# Signing Guide

This section uses Visual Studio as an example to describe how to integrate the C# SDK for API request signing. You can import the sample project in the code package, and integrate the signing SDK into your application by referring to the API calling example.

Preparing the Environment

Download Visual Studio 2019 16.8.4 or later from the Visual Studio official website and install it.

Obtaining the SDK

The following table shows the directory structure of the downloaded package.

Name	Description
apigateway-signature\Signer.cs	SDK code
apigateway-signature\HttpEncoder.cs	SDK code
sdk-request\Program.cs	Sample code for signing requests
csharp.sln	Project file
licenses\license-referencesource	Third-party license

Opening the Sample Project

Double-click csharp.sln in the SDK package to open the project. The project contains the following:

apigateway-signature: Shared library that implements the signature algorithm. It can be used in the .Net Framework and .Net Core projects.
backend-signature: Example of a backend service signature.
sdk-request: Example of invoking the signature algorithm. Modify the parameters as required.

Request Signing and API Calling

After the calling information is modified, the sample code can be directly called. For details about the calling information, see Preparations.

Import the SDK to the project.

      
           using System;
using System.Net;
using System.IO;
using System.Net.Http;
using System.Threading;
using APIGATEWAY_SDK;

Generate a new signer and enter the AK and SK.

In this example, the AK and SK stored in the environment variables are used. Specify the environment variables CLOUD_SDK_AK and CLOUD_SDK_SK in the local environment first. The following uses Linux as an example to describe how to set the obtained AK/SK as environment variables.
1. Open the terminal and run the following command to open the environment variable configuration file:
  vi ~/.bashrc
2. Set environment variables, save the file, and exit the editor.
```
export CLOUD_SDK_AK="Obtained AK"
export CLOUD_SDK_SK="Obtained SK"
```
3. Run the following command to apply the modification:
  source ~/.bashrc

Generate a new signer and enter the configured environment variables.

        
             Signer signer = new Signer();
signer.Key = Environment.GetEnvironmentVariable("CLOUD_SDK_AK");
signer.Secret = Environment.GetEnvironmentVariable("CLOUD_SDK_SK");

Generate a new request, and specify the domain name, method, request URI, and body.

      
           //The following example shows how to set the request URL and parameters to query a VPC list.
HttpRequest r = new HttpRequest("GET", new Uri("https://{service}.region.example.com/v1/77b6a44cba5**********9a8ff44fd/vpcs?limit=1"));
//Add a body if you have specified the PUT or POST method. Special characters, such as the double quotation mark ("), contained in the body must be escaped.
r.body = "";

Add other headers required for request signing or other purposes. For example, add the x-stage header for API environment, X-Project-Id header in multi-project scenarios or the X-Domain-Id header for a global service.

      
           r.headers.Add("x-stage", "RELEASE");
r.headers.Add("X-Project-Id", "xxx");
r.headers.Add("X-Domain-Id", "xxx");
//Add header parameters, for example, X-Domain-Id for invoking a global service and X-Project-Id for invoking a project-level service.

Execute the following function to generate HttpWebRequest, and add the X-Sdk-Date and Authorization headers for signing the request:
If you use HttpClient, you can obtain header information from the request. For details about headers, see API Signature Authentication Mechanism.
1

HttpWebRequest req = signer.Sign(r);

Access the API and view the access result.

      
       
         
         
           try
{
    var writer = new StreamWriter(req.GetRequestStream());
    writer.Write(r.body);
    writer.Flush();
    HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
    var reader = new StreamReader(resp.GetResponseStream());
    Console.WriteLine(reader.ReadToEnd());
}
catch (WebException e)
{
    HttpWebResponse resp = (HttpWebResponse)e.Response;
    if (resp != null)
    {
        Console.WriteLine((int)resp.StatusCode + " " + resp.StatusDescription);
        var reader = new StreamReader(resp.GetResponseStream());
        Console.WriteLine(reader.ReadToEnd());
    }
    else
    {
        Console.WriteLine(e.Message);
    }
}
Console.WriteLine("----------------");

          

        

      
     