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docs/core/multidbs.md

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+# 配置多数据库
+
+框架支持同时访问多个数据库。具体操作如下：
+
+## 添加新数据库连接字符串
+
+在配置文件appsettings.json中，添加新的连接字符串`OpenAuthDBContext2`
+
+```csharp
+ "ConnectionStrings": {
+    "OpenAuthDBContext": "Data Source=.;Initial Catalog=OpenAuthPro;User=sa;Password=000000",
+    "OpenAuthDBContext2": "Data Source=.;Initial Catalog=OpenAuthDB;User=sa;Password=000000"
+  }
+ "AppSetting": {
+    "DbTypes": {
+        "OpenAuthDBContext":"SqlServer"   //数据库类型：SqlServer、MySql、Oracle
+       ,"OpenAuthDBContext2":"SqlServer"  //链接字符串OpenAuthDBContext2对应的数据库类型
+    }
+  }
+```
+
+## 添加新的数据上下文
+
+在OpenAuth.Repository中添加新的数据库上下文，比如`OpenAuthDBContext2`
+
+```csharp
+public class OpenAuthDBContext2 : DbContext
+    {
+        private IConfiguration _configuration;
+        private ILoggerFactory _LoggerFactory;
+        private const string _connectstr = "OpenAuthDBContext2";
+        
+        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+        {
+            optionsBuilder.UseLoggerFactory (_LoggerFactory);
+
+             string connect = _configuration.GetConnectionString(_connectstr);
+            if (string.IsNullOrEmpty(connect))
+            {
+                throw new Exception($"未能找到{_connectstr}对应的连接字符串信息");
+            }
+
+            //这个地方如果用IOption，在单元测试的时候会获取不到AppSetting的值😅
+            var dbtypes = _configuration.GetSection("AppSetting:DbTypes").GetChildren()
+                .ToDictionary(x => x.Key, x => x.Value);
+            
+            var dbType = dbtypes[_connectstr];
+            if (dbType == Define.DBTYPE_SQLSERVER)
+            {
+                optionsBuilder.UseSqlServer(connect);
+            }
+            else if(dbType == Define.DBTYPE_MYSQL)  //mysql
+            {
+                optionsBuilder.UseMySql(connect);
+            }
+            else
+            {
+                optionsBuilder.UseOracle(connect);
+            }
+
+            base.OnConfiguring (optionsBuilder);
+        }
+        
+        public OpenAuthDBContext2(DbContextOptions<OpenAuthDBContext2> options, 
+        ILoggerFactory loggerFactory,IConfiguration configuration)
+            : base(options)
+        {
+            _LoggerFactory = loggerFactory;
+            _configuration = configuration;
+        }
+
+        ... //其他代码请参考OpenAuthDbContext
+    }
+
+```
+
+## 注入新数据库
+
+在项目（OpenAuth.WebApi等）的启动代码`Startup.cs`中，注入刚刚添加的数据库
+
+```csharp
+ services.AddDbContext<OpenAuthDBContext2>();
+```
+
+## 编写业务代码
+
+我们以系统日志模块为例，只需要调整以下代码，然后运行就可以发现，日志已经全部记录到新的数据库中。
+
+```csharp
+  public class SysLogApp : BaseApp<SysLog,OpenAuthDBContext2>
+    {
+        public SysLogApp(IUnitWork<OpenAuthDBContext2> unitWork, IRepository<SysLog,OpenAuthDBContext2> repository) : base(unitWork, repository, null)
+        {
+        }
+
+        ...//剩余的代码和系统自带的模块完全一致
+    }
+```