Linq to SQL connection String to read from web.config file automatically

When we use Linq to SQL it creates a connection string in Settings files. When we need to create the DLL of the DataAccessLayer (DAL) for production server or any server which is not our current development server then we need to change connection string manually in Settings file, is not it would be good to set something in application so it can always read the connection string form web.config file automatically? Is it possible? yes, and it's quite easy. Let me explain how we can achieve it.

If you will look your DataContext.designer.cs file, it will look like

public partial class MyDataContext : System.Data.Linq.DataContext
       private static System.Data.Linq.Mapping.MappingSource mappingSource = 
                          new AttributeMappingSource();
       // close Extensibility Method Definitions region
       public MyDataContext() : 
                   base(global::MyLib.Library.DAL.Properties.Settings.Default.MyDBConnectionString1, mappingSource)

      public MyDataContext(string connection) : base(connection, mappingSource)

All the above code is auto generated so you don't have to vary to understand each and every line here.

We know our DataContext class name, in this example it is "MyDataContext", right.

Now what we need is to create a partial class with the same name "MyDataContext" to override the OnCreate method and assign the connection string from web.config that's it, so let's create the class.

    public partial class MyDataContext
        partial void OnCreated()
            this.Connection.ConnectionString =       

That's it, and here is the connection string in web.config file.

    <add name="MyDBConnectionString" 
            connectionString="data source=(local);
            initial catalog=NorthWind; 

If you will run the application it will automatically read the connection string form web.config file.

Note: if more than one people are working on the same project and when they will drag and drop new tables it will show an error:

base(global::MyLib.Library.DAL.Properties.Settings.Default.MyDBConnectionString1 doesn't exist, in that case you don't have to worry, replace entire "global::MyLib.Library.DAL.Properties.Settings.Default.MyDBConnectionString1" string to blank ("") string because you are not reading connection string for setting file any more.

Montana Neyra
  • linq to sql
  • web.config
By Montana Neyra On 17 Jun, 12  Viewed: 3,369

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