如何配置.NET Aspire测试使用launchSettings.json指定端口？

我目前在使用.NET Aspire，所有项目都能正常运行，现在正在创建测试，希望确保每个项目运行在其launchSettings.json中定义的端口，而不是随机端口。当前的测试代码如下：

var appHost = await DistributedApplicationTestingBuilder.CreateAsync<Aspire_AppHost>();

appHost.Services.ConfigureHttpClientDefaults(clientBuilder =>
{
    clientBuilder.AddStandardResilienceHandler();
});

var app = await appHost.BuildAsync();
await app.StartAsync();

var http = App.CreateHttpClient("myApi");
string url = http.BaseAddress.Authority;

现在url被分配了带随机端口的localhost，请问该如何配置测试设置以使用launchSettings.json中的正确端口？

解决方法 #

要让Aspire测试使用launchSettings.json里的固定端口，需要在测试代码中显式加载并应用launchSettings的配置，具体步骤如下：

1. 读取launchSettings.json配置 #

在测试项目中，添加代码读取目标项目的launchSettings.json文件，解析出对应的端口配置。假设你的API项目位于../MyApi目录下：

using System.Text.Json;

// 读取目标项目的launchSettings.json
var launchSettingsPath = Path.Combine(Directory.GetCurrentDirectory(), "../MyApi/Properties/launchSettings.json");
var launchSettingsJson = await File.ReadAllTextAsync(launchSettingsPath);
var launchSettings = JsonDocument.Parse(launchSettingsJson).RootElement;

// 提取指定配置的HTTPS端口（可根据需求切换为HTTP）
var httpsPort = launchSettings.GetProperty("profiles")
                               .GetProperty("MyApi")
                               .GetProperty("applicationUrl")
                               .GetString()
                               ?.Split(';')
                               .First(u => u.StartsWith("https://"))
                               .Split(':')
                               .Last();

2. 在Aspire测试中覆盖服务端口配置 #

通过DistributedApplicationTestingBuilder的配置，为目标服务指定固定端口：

var appHost = await DistributedApplicationTestingBuilder.CreateAsync<Aspire_AppHost>();

// 为myApi服务配置固定端口
if (!string.IsNullOrEmpty(httpsPort))
{
    appHost.Services.Configure<ServiceEndpointOptions>("myApi", options =>
    {
        options.Port = int.Parse(httpsPort);
        options.Scheme = "https";
    });
}

appHost.Services.ConfigureHttpClientDefaults(clientBuilder =>
{
    clientBuilder.AddStandardResilienceHandler();
});

var app = await appHost.BuildAsync();
await app.StartAsync();

var http = App.CreateHttpClient("myApi");
string url = http.BaseAddress.Authority; // 此时将使用launchSettings中定义的固定端口

3. 可选：封装通用读取方法 #

如果多个项目需要处理，可以封装一个通用方法来复用端口读取逻辑：

private static async Task<int> GetLaunchSettingsPort(string projectRelativePath, string profileName, string scheme = "https")
{
    var launchSettingsPath = Path.Combine(Directory.GetCurrentDirectory(), projectRelativePath, "Properties/launchSettings.json");
    var launchSettingsJson = await File.ReadAllTextAsync(launchSettingsPath);
    var launchSettings = JsonDocument.Parse(launchSettingsJson).RootElement;
    
    var appUrl = launchSettings.GetProperty("profiles")
                               .GetProperty(profileName)
                               .GetProperty("applicationUrl")
                               .GetString();
    
    if (string.IsNullOrEmpty(appUrl))
        throw new InvalidOperationException("未找到有效的applicationUrl配置");
    
    var targetUrl = appUrl.Split(';').First(u => u.StartsWith($"{scheme}://"));
    return int.Parse(targetUrl.Split(':').Last());
}

调用示例：

var apiPort = await GetLaunchSettingsPort("../MyApi", "MyApi");

appHost.Services.Configure<ServiceEndpointOptions>("myApi", options =>
{
    options.Port = apiPort;
    options.Scheme = "https";
});

内容的提问来源于stack exchange，提问作者man developer