C#

Scenarios

To use C# to call an API through app authentication, obtain the C# SDK, open the project file in the SDK, and then call the API by referring to the API calling example.

Prerequisites

You have obtained API calling information. For details, see Preparation.
You have installed Visual Studio 2019 version 16.8.4 or a later version. If not, download it from the official Visual Studio website and install it.

Obtaining the SDK

Log in to the APIG console, and download the SDK on the SDKs page by referring to section "SDKs" in the API Gateway User Guide.

Alternatively, download the latest SDK version. Then obtain the ApiGateway-csharp-sdk.zip package. The following table shows the files decompressed from the package.

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

Opening a 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. For details about the sample code, see API Calling Example.

API Calling Example

Import the C# SDK to your project.
1

using APIGATEWAY_SDK;

Generate a new signer and enter the AppKey and AppSecret.

In this example, the AK and SK stored in the environment variables are used. Specify the environment variables HUAWEICLOUD_SDK_AK and HUAWEICLOUD_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 HUAWEICLOUD_SDK_AK="Obtained AK"
export HUAWEICLOUD_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();
// Directly writing AK/SK in code is risky. For security, encrypt your AK/SK and store them in the configuration file or environment variables.
// In this example, the AK/SK are stored in environment variables for identity authentication. Before running this example, set environment variables HUAWEICLOUD_SDK_AK and HUAWEICLOUD_SDK_SK.
signer.Key = Environment.GetEnvironmentVariable("HUAWEICLOUD_SDK_AK");
signer.Secret = Environment.GetEnvironmentVariable("HUAWEICLOUD_SDK_SK");

Generate an HttpRequest, and specify the method, request URL, and body.

      
           HttpRequest r = new HttpRequest("POST",    
                    new Uri("https://c967a237-cd6c-470e-906f-a8655461897e.apigw.exampleRegion.com/app1?query=value"));
r.body = "{\"a\":1}";

Add the x-stage header to the request to specify an environment name. Add other headers to be signed as necessary.
1

r.headers.Add("x-stage", "RELEASE");
Execute the following function to generate HttpWebRequest, and add the X-Sdk-Date and Authorization headers for signing the request:
1

HttpWebRequest req = signer.Sign(r);

Access the API and view the access result.

      
           var writer = new StreamWriter(req.GetRequestStream());
writer.Write(r.body);
writer.Flush();
HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
var reader = newStreamReader(resp.GetResponseStream());
Console.WriteLine(reader.ReadToEnd());