Getting sql connection string from web.config file

[Scarshady]

I am learning to write into a database from a textbox with the click of a button. I have specified the connection string to my NorthWind database in my \[code\]web.config\[/code\] file. However I am not able to access the connection string in my code behind. This is what I have tried.\[code\]protected void buttontb_click(object sender, EventArgs e){ System.Configuration.Configuration rootwebconfig = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("/Mohtisham"); System.Configuration.ConnectionStringSettings constring; constring = rootwebconfig.ConnectionStrings.ConnectionStrings["northwindconnect"]; SqlConnection sql = new SqlConnection(constring); sql.Open(); SqlCommand comm = new SqlCommand("Insert into categories (categoryName) values ('" + tb_database.Text + "')", sql); comm.ExecuteNonQuery(); sql.Close();}\[/code\]I get a tooltip error for \[code\]SqlConnection sql = new SqlConnection(constring);\[/code\]as\[quote\] System.data.SqlClient.Sqlconnection.Sqlconnection(string) has some invalid arguments.\[/quote\]I want to load the connection string from the \[code\]web.config\[/code\] in \[code\]constring\[/code\]