Connecting to local SQL Server database using C#

Suppose I have created a SQL Server database called Database1.mdf in the App_Data folder in Visual Studio with a table called Names.

How could I establish a connection to read the table values using C#?

So far I've tried something like this:

SqlConnection conn = new SqlConnection("Server=localhost;Database=Database1;");

conn.Open();

// create a SqlCommand object for this connection
SqlCommand command = conn.CreateCommand();
command.CommandText = "Select * from Names";

But I get an error:

database not found/error connecting to database