实体框架在运行时更改连接 [英] Entity Framework change connection at runtime

问题描述

我有一个Web API项目引用我的模型和DAL程序集。用户将看到一个登录屏幕，他可以在其中选择不同的数据库。

我建立了如下连接字符串：

  public void Connect（数据库数据库）
 {
 //构建SQL连接字符串
 SqlConnectionStringBuilder sqlString = new SqlConnectionStringBuilder（）
 {
 DataSource = database.Server，
 InitialCatalog = database.Catalog，
 UserID = database.Username，
 Password = database.Password，
}; 
 
 //构建一个实体框架连接字符串
 EntityConnectionStringBuilder entityString = new EntityConnectionStringBuilder（）
 {
 Provider = database.Provider，
 Metadata = Settings。 Default.Metadata，
 ProviderConnectionString = sqlString.ToString（）
}; 
} 
  

首先，我如何实际改变数据上下文的连接？

其次，由于这是一个Web API项目，所以连接字符串（在上面登录时设置）在用户交互中持续存在，或者每次都要传递给我的数据上下文？

解决方案

这个答案有点迟了，但我认为有一个潜在的方法来做一个整洁的小扩展方法。我们可以利用EF配置加上几个框架调用。

无论如何，注释的代码和示例用法：

扩展方法类：

  public static class ConnectionTools 
 {
 // all params是可选的
 public static void ChangeDatabase（
 this DbContext source，
 string initialCatalog =，
 string dataSource =，
 string userId = 
 string password =，
 bool integratedSecuity = true，
 string configConnectionStringName =）
 / *如果
 * connectionString名称从
 *基础EF类名* / 
 {
 try 
 {
 //如果它不为空，则使用const名称，否则
 //使用连接字符串的约定= EF contextname 
 //获取类型名称a d我们完成
 var configNameEf = string.IsNullOrEmpty（configConnectionStringName）
？ source.GetType（）。Name 
：configConnectionStringName; 
 
 //添加对System.Configuration的引用
 var entityCnxStringBuilder = new EntityConnectionStringBuilder 
（System.Configuration.ConfigurationManager 
 .ConnectionStrings [configNameEf] .ConnectionString）; 
 
 //初始化具有完整EF连接字符串货物的sqlbuilder 
 var sqlCnxStringBuilder = new SqlConnectionStringBuilder 
（entityCnxStringBuilder.ProviderConnectionString）; 
 
 //仅在添加
时填充参数（如果（！string.IsNullOrEmpty（initialCatalog））
 sqlCnxStringBuilder.InitialCatalog = initialCatalog; 
 if（！string.IsNullOrEmpty（dataSource））
 sqlCnxStringBuilder.DataSource = dataSource; 
 if（！string.IsNullOrEmpty（userId））
 sqlCnxStringBuilder.UserID = userId; 
 if（！string.IsNullOrEmpty（password））
 sqlCnxStringBuilder.Password = password; 
 
 //设置集成安全状态
 sqlCnxStringBuilder.IntegratedSecurity = integratedSecuity; 
 
 //现在翻转已更改的属性
 source.Database.Connection.ConnectionString 
 = sqlCnxStringBuilder.ConnectionString; 
} 
 catch（Exception ex）
 {
 //设置日志项目如果需要
} 
} 
} 
  

基本用法：

  //假定.config中的一个connectionString名称为MyDbEntities 
 var selectedDb = new MyDbEntities（）; 
 //所以只引用更改的属性
 //使用对象参数名称
 selectedDb.ChangeDatabase 
（
 initialCatalog：name-of-another-initialcatalog ，
 userId：jackthelady，
密码：nomoresecrets，
 dataSource：@。\sqlexpress//可以是ip地址120.273.435.167等
） ; 
  

我知道你已经有基本的功能，但是认为这会增加一点点多样性。 / p>

I have a web API project which references my model and DAL assemblies. The user is presented with a login screen, where he can select different databases.

I build the connection string as follows:

    public void Connect(Database database)
    {
        //Build an SQL connection string
        SqlConnectionStringBuilder sqlString = new SqlConnectionStringBuilder()
        {
            DataSource = database.Server,
            InitialCatalog = database.Catalog,
            UserID = database.Username,
            Password = database.Password,
        };

        //Build an entity framework connection string
        EntityConnectionStringBuilder entityString = new EntityConnectionStringBuilder()
        {
            Provider = database.Provider,
            Metadata = Settings.Default.Metadata,
            ProviderConnectionString = sqlString.ToString()
        };
    }

First of all, how do I actually change the connection of the data context?

And secondly, as this is a web API project, is the connection string (set at login per above) persistent throughout the user's interaction or should it be passed every time to my data context?

解决方案

A bit late on this answer but I think there's a potential way to do this with a neat little extension method. We can take advantage of the EF convention over configuration plus a few little framework calls.

Anyway, the commented code and example usage:

extension method class:

public static class ConnectionTools
{
    // all params are optional
    public static void ChangeDatabase(
        this DbContext source,
        string initialCatalog = "",
        string dataSource = "",
        string userId = "",
        string password = "",
        bool integratedSecuity = true,
        string configConnectionStringName = "") 
        /* this would be used if the
        *  connectionString name varied from 
        *  the base EF class name */
    {
        try
        {
            // use the const name if it's not null, otherwise
            // using the convention of connection string = EF contextname
            // grab the type name and we're done
            var configNameEf = string.IsNullOrEmpty(configConnectionStringName)
                ? source.GetType().Name 
                : configConnectionStringName;

            // add a reference to System.Configuration
            var entityCnxStringBuilder = new EntityConnectionStringBuilder
                (System.Configuration.ConfigurationManager
                    .ConnectionStrings[configNameEf].ConnectionString);

            // init the sqlbuilder with the full EF connectionstring cargo
            var sqlCnxStringBuilder = new SqlConnectionStringBuilder
                (entityCnxStringBuilder.ProviderConnectionString);

            // only populate parameters with values if added
            if (!string.IsNullOrEmpty(initialCatalog))
                sqlCnxStringBuilder.InitialCatalog = initialCatalog;
            if (!string.IsNullOrEmpty(dataSource))
                sqlCnxStringBuilder.DataSource = dataSource;
            if (!string.IsNullOrEmpty(userId))
                sqlCnxStringBuilder.UserID = userId;
            if (!string.IsNullOrEmpty(password))
                sqlCnxStringBuilder.Password = password;

            // set the integrated security status
            sqlCnxStringBuilder.IntegratedSecurity = integratedSecuity;

            // now flip the properties that were changed
            source.Database.Connection.ConnectionString 
                = sqlCnxStringBuilder.ConnectionString;
        }
        catch (Exception ex)
        {
            // set log item if required
        }
    }
}

basic usage:

// assumes a connectionString name in .config of MyDbEntities
var selectedDb = new MyDbEntities();
// so only reference the changed properties
// using the object parameters by name
selectedDb.ChangeDatabase
    (
        initialCatalog: "name-of-another-initialcatalog",
        userId: "jackthelady",
        password: "nomoresecrets",
        dataSource: @".\sqlexpress" // could be ip address 120.273.435.167 etc
    );

I know you already have the basic functionality in place, but thought this would add a little diversity.

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