Exception when trying to connect to .sdf database

I have database in file C:\Users\Pawel\Documents\DB.sdf. How can I connect to it?

Simple code below does not work and generates exception.

Code:

[WebMethod]
public String TestCon()
{
    SqlConnection sql = new System.Data.SqlClient.SqlConnection(
        @"Data Source=C:\Users\Pawel\Documents\DB.sdf");

    string str = "OK";

    try
    {
        sql.Open();
        sql.Close();
    }
    catch (Exception ex)
    {
        str = ex.Message;
    }

    return str;
}

Result:

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify开发者_如何学Go that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

What am I missing? What I should do to open connection correctly?

EDIT:

System.NotSupportedException: SQL Server Compact is not intended for ASP.NET development.

Great :P

Consider using System.Data.SqlServerCe.SqlCeConnection:

System.Data.SqlServerCe.SqlCeConnection con = 
   new System.Data.SqlServerCe.SqlCeConnection(@"Data Source=C:\Users\Pawel\Documents\DB.sdf");

(Add a reference to System.Data.SqlServerCe, if necessary)

Also, to use it with ASP.NET, add:

AppDomain.CurrentDomain.SetData("SQLServerCompactEditionUnderWebHosting", true);

Apparently, you are using a SQL Compact Edition (sdf file). Have you tried using SqlCeConnection instead of SqlConnection ?

As a bonus: if you dont want to mess with connectionstrings anymore, please try this.

Do do so, you have to add a reference to System.Data.SqlServerCe assembly.