Environment.NewLine or "\n" or "\r\n" not work with TextBox in aspx.cs by c# in Web.Net

Question

I'm a beginner in c#, I use visual studio Web.Net to test some code:

protected void Page_Load(object sender, EventArgs e)

//String
          string x = "Welcome in C#";
          string y = "String =" + " " + x; 

//int
            int a = 27;
            int b = 3;
            int c = a / b;

//Float 7 digit 32bit
                      float f1 = 1/6f;

//Double 15-16 digits 64bit
                            double do1 = 1/6d;


//Decimal 28-29 digits 128bit
                              decimal de1 = 1/6m;

string nline = Environment.NewLine;
TextBox1.Text = y 
                + nline + "int =" + " " + c.ToString() 
                + nline + "float 7 digit =" + " " + f1.ToString() 
                + nline + "Double 15-16 digits =" + " " + do1.ToString() 
                + nline + "Decimal 28-29 digits =" + " " + de1.ToString();

Output in Browser: all in TextBox1 in one Line like image.

enter image description here