asp.net core api 跨域配置

项目前后端分离，前端请求接口例如使用axios发送请求时浏览器会提示跨域错误，需要后端配置允许接口跨域

配置步骤：

1、通过NuGet安装Microsoft.AspNetCore.Cors.dll类库

2、在Startup.cs中的ConfigureServices方法加入以下配置

            services.AddCors(options =>
            {
                options.AddPolicy("CorsPolicy", builder =>
                {
                    //builder.AllowAnyOrigin(); //客户端不携带cookie时，可以配置
                    builder.WithOrigins(ConfigHelper.GetSectionModel<List<string>>("CorsOrigins").ToArray()); //客户端携带cookie、或者在请求报文定义其他字段属性时，必须指定域名
                    builder.AllowAnyHeader();
                    builder.AllowAnyMethod();
                    builder.AllowCredentials();
                    builder.SetPreflightMaxAge(TimeSpan.FromSeconds(60));  //如果接口已验证过一次跨域，则在60分钟内再次请求时，将不需要验证跨域
                });

            });

3、在Startup.cs中的Configure方法加入以下配置

 app.UseCors("CorsPolicy");

注意：必须要加在app.UseMvc();前面

4、在appsettings.json配置可以跨域的域名：

"CorsOrigins": [ "http://www.testseparateapi.com:8080", "http://localhost:8080" ]


ConfigHelper读取appsettings.json工具类代码：

 1     /// <summary>
 2     /// appsettings.json配置文件帮助类
 3     /// </summary>
 4     public class ConfigHelper
 5     {
 6         static ConfigHelper()
 7         {
 8             Microsoft.Extensions.Configuration.IConfiguration config = AutofacHelper.GetService<Microsoft.Extensions.Configuration.IConfiguration>();
 9             if (config == null)
10             {
11                 var builder = new Microsoft.Extensions.Configuration.ConfigurationBuilder().SetBasePath(AppContext.BaseDirectory).AddJsonFile("appsettings.json");
12 
13                 config = builder.Build();
14             }
15 
16             _config = config;
17         }
18 
19         private static Microsoft.Extensions.Configuration.IConfiguration _config { get; }
20 
21         #region 从appsettings.json获取key的值
22         /// <summary>
23         /// 从appsettings.json获取key的值
24         /// 
25         /// 列如：appsettings.json的格式如下
26         /// 
27         /// {
28         ///  
29         ///  "Logging": {
30         ///    "LogLevel": {
31         ///      "Default": "Warning"
32         ///    }
33         ///},
34         ///  "AllowedHosts": "*",
35         ///  "RabbitMQ": {
36         ///    "HostName": "111",
37         ///    "UserName": "11",
38         ///    "Password": "11",
39         ///    "ReTryCount": "5"
40         ///  }
41         ///}
42         ///
43         /// 取RabbitMQ下的HostName的值，则参数key为 RabbitMQ:HostName
44         /// 
45         /// </summary>
46         /// <param name="key">key</param>
47         /// <returns></returns>
48         public static string GetValue(string key)
49         {
50             var rr = _config.GetSection(key).GetChildren();
51 
52             return _config[key];
53         }
54         #endregion
55 
56         #region appsettings.json 子节点转实体
57         /// <summary>
58         /// appsettings.json 子节点转实体
59         /// </summary>
60         /// <typeparam name="T"></typeparam>
61         /// <param name="key">节点名称</param>
62         /// <returns></returns>
63         public static T GetSectionModel<T>(string key) where T : new()
64         {
65             var model = new T();
66             _config.GetSection(key).Bind(model);
67             return model;
68         }
69 
70         #endregion
71 
72         /// <summary>
73         /// 获取连接字符串
74         /// </summary>
75         /// <param name="nameOfCon">连接字符串名</param>
76         /// <returns></returns>
77         public static string GetConnectionString(string nameOfCon)
78         {
79             return _config.GetConnectionString(nameOfCon);
80         }
81     }

配置允许所有域名通过跨域，builder.AllowAnyOrigin()，客户端请求的时候携带cookie或者其他参数的时候出现以下错误，必须通过builder.WithOrigins()指定域名