ASP.NET alert newline from CodeBehind

Question

I have such code in Page.aspx.cs file:

void btnSessionCreate_Click(object sender, EventArgs e)
{
        if (Session["user"] == null)
        {
            Session["user"] = Guid.NewGuid().ToString();
            Response.Redirect("/");
        }
        else if (Session["user"] != null)
        {
            string userBrowser = Request.UserAgent.ToString();
            string sessionId = Session["user"].ToString();

            Response.Write("<script>alert('" + sessionId + "\r\n" + userBrowser + "');</script>");
        }
 }

The main problem is "\r\n" part in Response.Write() method. I wanted to separate data with a newline, but can't!

If there is not "\r\n" , script alerts well, but if exists in code nothing is alerting and is changing resets its CSS style.

Why?

Answer 1

Use the @ symbol or double \\ to escape the slash

string script = String.Format(@"<script>alert('{0}\r\n{1}');</script>", sessionId, userBrowser);

OR

string script = String.Format("<script>alert('{0}\\r\\n{1}');</script>", sessionId, userBrowser);

Client.RegisterStartupScript(this.GetType(), "myscript", script, true);

More info on Client.RegisterStartupScript here

Answer 2

You just need to escape the \, so they become \ when output to JavaScript:

Response.Write("<script>alert('" + sessionId + "\\r\\n" + userBrowser + "');</script>");

Or:

Response.Write("<script>alert('" + sessionId + @"\r\n" + userBrowser + "');</script>");

You are in a C# context in the above line, so \r\n is interpreted as a new line that needs to be output by Response.Write. that's not what you want. You want the literal \r\n to be output, so they are interpreted as JavaScript newlines.