Creating An SQL Connection String And Inserting New Rows.

I am ultra new to this so thanks in advance for any help.

I was trying to create a connection to a database that I created in SQL Express. I am essentially trying to submit three attributes to the existing database from a table that consists of three textboxes and a submit button. I would like all of the code to be in the head of the page (because that is the standard here) so I wanted to know what the connection string should be in Visual Basic 2005 Express to establish a connection on the same machine. I'm not sure about the connection string, but I am also not sure about a lot of the code. Also, the Using clauses seem to give me an error (where should it go?). This is what I have in the head of the page (visual C# by the way). Also, I got this from http://www.csharp-station.com/Tutorials/AdoDotNet/Lesson03.aspx :

Using System.Data;
Using System.Data.SqlClient;

protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection conn = new SqlConnection("Data Source=(local);Database=CustomersDB;Trusted Connection=true");
conn.Open();
string insertstring = @" insert into Catagories (CustomerID, CustomerName, CustomerEmail) values (" + textbox1.value + ", " + textbox2.value + " + ", textbox3.value");
SqlCommand cmd = new SqlCommand(insertstring, conn);
Sql.ExecuteNonQuery();
conn.close();
}

If there is absolutely any insite into the problems with my code, I really appreciate it.