我们如何在 Web.Config 中有两个连接字符串并在后面的代码中在它们之间切换？

Question

When I add two connection strings in the web.config, an error appears that tells me I can't add two connection strings in the web.config.

I want the upper job because I have 2 databases and I want transfer data from another to the other one.

Would you please show me a way for doing that?

Answer 1

When you add a connection string, you name it.

You can access each such connection string and assign it to a different variable, passing that connection string to your data access layer.

In the config file:

<connectionStrings>

  <add name="Sales" 
       providerName="System.Data.SqlClient"
       connectionString= "server=myserver;database=Products;uid=<user name>;pwd=<secure password>" />

  <add name="NorthWind" 
       providerName="System.Data.SqlClient" 
       connectionString="server=.;database=NorthWind;Integrated Security=SSPI" />

</connectionStrings>

In your code:

 var conn1 = ConfigurationManager.ConnectionStrings["Sales"].ConnectionString;
 var conn2 = ConfigurationManager.ConnectionStrings["NorthWind"].ConnectionString;

Answer 2

Simply put those strings in your web.config:

<connectionStrings>
    <add name="CS1"
         connectionString="SOME CONNECTION STRING"
         providerName="System.Data.SqlClient" />
    <add name="CS2"
         connectionString="SOME OTHER STRING"
         providerName="System.Data.SqlClient" />
</connectionStrings>

And then pick the one you wish in your code:

string cs = ConfigurationManager.ConnectionStrings["CS2"].ConnectionString;

Answer 3

We can declare multiple connection strings under Web.Config or App.Config:

<connectionStrings>
    <add name="SourceDB" connectionString="..." />
    <add name="DestinationDB" connectionString="..." />
</connectionStrings>

In DAL you can access connection strings according to your requirements:

string SounceConnection = ConfigurationManager.ConnectionStrings["SourceDB"].ConnectionString;
string DestinationConnection = ConfigurationManager.ConnectionStrings["DestinationDB"].ConnectionString;

Answer 4

You can add all the connectionstrings that you want to web.config. But they must have different names.

Answer 5

Strange, because you can specify multiple connection strings. They simply must have different names.

Answer 6

Here are the steps:

 public class KisanDbContext : DbContext
    {
        public KisanDbContext() : base(nameOrConnectionString: "DbContext") { }
        public KisanDbContext(string conn) : base(nameOrConnectionString: conn) { }
    }

Access methods:

 private readonly KisanDbContext db;
 private readonly KisanDbContext db_old;
   

Inside your constructor:

public className()
{
    db = new KisanDbContext();
    db_old = new KisanDbContext("DbContextBackup");
}

This one is for your default connection.

public KisanDbContext() : base(nameOrConnectionString: "DbContext") { }

And if you want your multiple database connection please used this convention, where you can pass multiple database connection strings using same dbcontext.

public KisanDbContext(string conn) : base(nameOrConnectionString: conn) { }

Remember to have your connection string with different name as:

<connectionStrings>
     <add name="DbContext" connectionString="Server=A;Database=ABC;User 
     Id=ccd;Password=***"  providerName="System.Data.SqlClient" />
    <add name="DbContextBackup" connectionString="B;Database=DEF;User Id=axx;Password=***;   
    providerName="System.Data.SqlClient" />  
</connectionStrings>