Change Entity Connection string on runtime

Question

I'm using entity framework 6.02 and Vb.net with Sql server databases.

I have 4 identical databases on 4 different servers.I create Entity through wizard with one of the databases.Now I want to modify the connection string on runtime , to connect with other databases.

This is how I do this change :

This is the connection string on app.config inside visual studio ( I have changed server name with {SERVER} and database name with {DATABASE}

<connectionStrings>
 <add name="MyEntities" connectionString="metadata=res://*/Model1.csdl|res://*/Model1.ssdl|res://*/Model1.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source={SERVER};initial catalog={DATABASE};integrated security=True;multipleactiveresultsets=True;application name=EntityFramework&quot;" providerName="System.Data.EntityClient" />
 </connectionStrings>

This is the code to change the connection string :

Public Cnstring as string

Dim connstringtemplate As String = System.Configuration.ConfigurationManager.ConnectionStrings(1).ConnectionString.ToString

Cnstring = connstringtemplate.Replace("{DATABASE}", "MyDB2").Replace("{SERVER}","PC2").Tostring

This is My Entity class to accept connection string as parameter :

Partial Public Class MyEntities
 Inherits DbContext   
Public Sub New(connectionString  As String)
     If String.IsNullOrWhiteSpace(connectionString) Then
          Throw New ArgumentNullException("connectionString")
     End If
     Database.Connection.ConnectionString = connectionString
 End  Sub

This is Entity declaration :

context = New MyEntities(cnstring)

But now on runtime i get an error on the line

Database.Connection.ConnectionString = connectionString
An unhandled exception of type 'System.ArgumentException' occurred in System.Data.dll

Additional information: Keyword not supported: 'metadata'.

What's wrong with this code ?

Thank you !

Where did you get that connection string from?

D.R.
– D.R.

2014-03-19 12:18:13 +00:00
Commented Mar 19, 2014 at 12:18 — D.R.
– D.R., Commented Mar 19, 2014 at 12:18
This connection string is inside app.config.

alex
– alex

2014-03-19 12:28:32 +00:00
Commented Mar 19, 2014 at 12:28 — alex
– alex, Commented Mar 19, 2014 at 12:28
Yes is auto-generated

alex
– alex

2014-03-19 12:40:02 +00:00
Commented Mar 19, 2014 at 12:40 — alex
– alex, Commented Mar 19, 2014 at 12:40

reckface · Accepted Answer · 2014-09-25 16:25:33Z

The DbContext constructor accepts a connection string as a parameter. You may be better off building a connection string and passing that to the constructor.

I have used something like:

// the model name in the app.config connection string (any model name - Model1?)
private static string GetConnectionString(string model, settings)
{
    // Build the provider connection string with configurable settings
    var providerSB = new SqlConnectionStringBuilder
    {
        InitialCatalog = settings.InitialCatalog,
        DataSource = settings.DataSource,
        UserID = settings.User,
        Password = settings.Password
    };

    var efConnection = new EntityConnectionStringBuilder();
    // or the config file based connection without provider connection string
    // var efConnection = new EntityConnectionStringBuilder(@"metadata=res://*/model1.csdl|res://*/model1.ssdl|res://*/model1.msl;provider=System.Data.SqlClient;");
    efConnection.Provider = "System.Data.SqlClient";
    efConnection.ProviderConnectionString = providerSB.ConnectionString;
    // based on whether you choose to supply the app.config connection string to the constructor
    efConnection.Metadata = string.Format("res://*/Model.{0}.csdl|res://*/Model.{0}.ssdl|res://*/Model.{0}.msl", model); ;
    return efConnection.ToString();

}

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