C#

Worksheet ws = m_wkbk.Sheets[1];
ws.Activate();

// Attempt 1
ws.Range["A1", "E1"].Style.Locked = true; // This runs but has no impact on the launched sheet.

// Attempt 2
Range range = (Range)ws.get_Range(ws.Cells[1, 1], ws.Cells[1, 5]); // Runtime error
range.Locked = true;

[{"msg":"","FeatureSlno":"2","Feature":"Fuel Used","DefaultValue":"","FeatureType":"B","Groups":"OverView","GroupOrder":"0","SubGroupOrder":"0","CategorySlno":"2","UtilisationSlno":"1","IconImagePath":"","LowerIsBetter":"0"},{"msg":"","FeatureSlno":"3","Feature":"Seating Capacity","DefaultValue":"","FeatureType":"B","Groups":"OverView","GroupOrder":"0","SubGroupOrder":"0","CategorySlno":"3","UtilisationSlno":"0","IconImagePath":"","LowerIsBetter":"0"}]

Hello All,
 
I am new to the language of C#. I am try to create a url 
 
public void button1_Click(object sender, EventArgs e)
{
string myip = textBox1.Text;
string password = textBox2.Text;
string username = textBox3.Text;
string at = "@";
string mystring = "http://" + at + username + password + myip + "/command.htm?key= ";
Process.Start(mystring);
 
The result of clicking the button is below in my browser: 
 
 http://adminpassword192.168.123.123/command.htm?key=
 
 How can I get the @ sign to show up in the url in the browser?
 
Any help would be greatly appreciated.
 
Kind