如何使用 C# 在运行时重写在 Web.config 文件中设置的数据库

尝试设置 DbConnection.ConnectionString 属性。

dataContextInstance.Database.Connection.ConnectionString = "new connection string";

但我不确定在更改连接字符串后是否需要重新初始化某些属性/代码。

你可以做这样的事情，这个 ExampleData 只是一个要理解的例子，你可以在这里计算你需要的值，你的连接字符串保持这样：

<connectionStrings>
        <add name="ConnectionString.Properties.Settings.CustomConnectionString"
            connectionString="Persist Security Info=True" providerName="System.Data.SqlClient" />
    </connectionStrings>

这只是初始化数据的示例 使用系统;

namespace ConnectionStringCustom
{
    public static class ExampleData
    {
        public static String connUserName = "user";
        public static String connPassword = "pass";
        public static String connServerName = "servername";
        public static String connDatabaseName = "databasename";
    }
}

namespace ConnectionStringCustom.Properties
   {
   internal sealed partial class Settings
      {

      void Settings_SettingsLoaded( object sender, System.Configuration.SettingsLoadedEventArgs e )
         {
             this["CustomConnectionString"] = "Data Source=" + ExampleData.connServerName + ";"
                                          + "Initial Catalog=" + ExampleData.connDatabaseName + ";"
                                          + "Persist Security Info=false;"
                                          + "User ID=" + ExampleData.strConnUserName + ";"
                                          + "Password=" + ExampleData.connPassword + ";";
         }
      }
   }

有了这个，您可以更改所有礼仪。

编辑：查看您的更改，我认为您可能需要类似的东西

https://stackoverflow.com/a/7692708/5842138

但我认为这不是一个好的做法，为什么你不简单地创建许多连接字符串？

希望这个帮助

我创建了一个 2 个上下文。

1. BaseContext：此上下文不会更改，我使用它来设计我的应用，使用代码优先方法。

2. 动态上下文：此上下文将在运行时更改。

为了使 DynamicContext 正常工作，我在连接文件中创建了一个动态连接。

我基本上把它添加到我的块中

<add name="DynamicConnection" connectionString="Server=DefaultServer;Initial Catalog=I3_IC;User ID=defaultUser; Password=defaultPassword;" providerName="System.Data.SqlClient" />

然后我创建了一个新的上下文类，如下所示

使用系统;使用 System.Collections.Generic;使用System.Data.Common;使用System.Data.Entity;使用 System.Data.Entity.Core.EntityClient;使用 System.Data.SqlClient;使用System.Linq;使用系统网;

namespace MyApp.DataAccessLayer
{
    public class DynamicContext : DbContext
    {
        protected string connectionName = "DynamicConnection";
        protected string myServerName;
        protected string myUserId;
        protected string myPassword;
        /**
         * Created the connection to the server using the giving connection string name.
         * This constructor will allow you to connect to any connection string found in the Web.config file
         * 
         * @param connName
         */
        public DynamicContext(string serverName = null, string userID = null, string password = null)
            : base("DynamicConnection")
        {
            myServerName = serverName;
            myUserId = userID;
            myPassword = password;
        }
        /**
         * This constructor will allow you to construct a context by giving a string and it can only be call from the class itself
         * 
         */
        private DynamicContext(string connectionString)
            : base(connectionString)
        {
        } 

        /**
         * Changes the default database
         * 
         * @param databaseName
         */
        public DynamicContext setDatabase(string databaseName)
        {
            //Get the existing string for dynamic connection
            var connectionString = System.Configuration.ConfigurationManager.ConnectionStrings[connectionName].ConnectionString;
            //convert the existsing string into an object
            SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder(connectionString);
            //change the database before creating the new connection
            builder.InitialCatalog = databaseName;
            if (myServerName != null){
                builder.DataSource = myServerName;
            }
            if (myUserId != null){
                builder.UserID = myUserId;
            }
            if (myPassword != null){
                builder.Password = myPassword;
            }
            return new DynamicContext(builder.ConnectionString);
        }
    }
}

然后我这样用这个

//Create a dynamic context, note that you can also change the username and the password of the default user by using the second and third parameters.
var dbDynamic = new DynamicContext(serverName);
//Finally, you can set the correct table
var conn1 = dbDynamic.setDatabase('table1');
//If you want to connect to a different table
var conn2 = dbDynamic.setDatabase('table2');