.NET 6通过Docker连接SQL Server时出现User ID为空异常

异常信息 #

2024-03-18 11:50:22 Unhandled exception. System.ArgumentNullException: Value cannot be null. (Parameter 'User ID')
2024-03-18 11:50:22 at Microsoft.Data.Common.ADP.CheckArgumentNull(Object value, String parameterName)
2024-03-18 11:50:22 at Microsoft.Data.SqlClient.SqlConnectionStringBuilder.SetValue(String keyword, String value)
2024-03-18 11:50:22 at Microsoft.Data.SqlClient.SqlConnectionStringBuilder.set_UserID(String value)
2024-03-18 11:50:22 at Program.$(String[] args) in Program.cs:line 22

配置文件（appsettings.Development.json） #

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "ConnectionStrings": {
    "SQLDbConnection": "Server=localhost,1433;Initial Catalog=db;",
  },
  "UserId": "sa",
  "Password": "passw0rd"
}

数据库连接代码（Program.cs） #

// Connect to server using connection string from appSettings.Development.json
var sqlConBuilder = new SqlConnectionStringBuilder();

sqlConBuilder.ConnectionString = builder.Configuration.GetConnectionString("SQLDbConnection");

// Use user ID and password directly from configuration
sqlConBuilder.UserID = builder.Configuration["UserId"];
sqlConBuilder.Password = builder.Configuration["Password"];

builder.Services.AddDbContext<AppDbContext>(opt => opt.UseSqlServer(sqlConBuilder.ConnectionString));

异常原因 #

异常提示User ID参数为null，说明代码中builder.Configuration["UserId"]未读取到配置值。Docker环境下常见原因包括：

• 未明确加载appsettings.Development.json配置文件
• 配置文件未被复制到Docker镜像中
• 运行时环境变量未正确覆盖配置值

解决方法 #

• 明确加载开发环境配置：在Program.cs开头添加配置加载代码，确保开发环境配置被读取：

  var builder = WebApplication.CreateBuilder(args);
  // 强制加载开发环境配置文件
  builder.Configuration.AddJsonFile("appsettings.Development.json", optional: false, reloadOnChange: true);
  

• 确保配置文件被复制到Docker镜像：在Dockerfile中添加复制指令，将配置文件同步到容器内：

  COPY ["appsettings.Development.json", "."]
  

• 验证环境变量配置：如果通过环境变量传递凭据，确保Docker运行时已设置对应变量，或在docker-compose.yml中配置：

  services:
    api:
      environment:
        - UserId=sa
        - Password=passw0rd
  

• 临时调试方案：直接在连接字符串中嵌入凭据，验证数据库连接是否正常：

  "ConnectionStrings": {
    "SQLDbConnection": "Server=localhost,1433;Initial Catalog=db;User ID=sa;Password=passw0rd;"
  }
  

内容的提问来源于stack exchange，提问作者MarkHughes88