Sql Server - Update Database Not Working

i have in asp.net a few textboxes and i wish to update my database with the values that they encapsulate. The problem is that it doesn't work and although it doesn't work, the syntax seems correct and there are no errors present . Here is my linkbutton:

<asp:linkbutton id="clickOnSave" runat="server"
onclick="Save_Click" Text="Save Profile" />

and my update function

protected void Save_Click(object sender, EventArgs e)
{
SqlConnection con = new System.Data.SqlClient.SqlConnection();
con.ConnectionString = "DataSource=.\SQLEXPRESS;AttachDbFilename=C:\Users\alex\Documents\seeubook_db.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True";
con.Open();
String commandString = "UPDATE users SET last_name='" + Text4.Text.Trim() + "' , first_name='" + Textbox1.Text.Trim() + "' , about_me='" + Textbox5.Text.Trim() + "' , where_i_live='" + Textbox2.Text.Trim() + "' , where_i_was_born='" + Textbox3.Text.Trim() + "' , work_place='" + Textbox4.Text.Trim() + "' WHERE email='" + Session["user"] + "'";
SqlCommand sqlCmd = new SqlCommand(commandString, con);
sqlCmd.ExecuteNonQuery();
con.Close();
}