Cryptography using RSA algorithm

See more:

C#

I want to encrypt and decrypt (using RSA algorithm) any string without using cryptography classes i wrote a code please tell me about my mistake where i do wrong....

protected void Button1_Click(object sender, EventArgs e)
{
    string ab;

    int unicode = 0, a = 0, cnt = 0, i = 0, j = 0;
    int[] number=new int[1000];
    double[] c1=new double[1000];
    double[] unicode1 = new double[1000];
     
    ab = TextBox1.Text;
    double d;

    foreach (char c in ab)
    {        
        unicode = c;
        Console.WriteLine(unicode < 128 ? ASCII:{0} : NON-ASCII:{0}, unicode);
        number[i] = unicode;
        i++;
    }
    
    double p = 0, q = 0, o = 0;

    p = (double)Convert.ToInt64(TextBox2.Text);
    q = (double)Convert.ToInt64(TextBox3.Text);
    
    double n = p * q;
    double q1 = (p - 1) * (q - 1);

    Response.Write(q1);

    o = (double)Convert.ToInt64(TextBox4.Text);
    d = (Math.Pow(o, -1));
    d = d % q1;
    
    for (j = 0; j< i; j++)
    {
        c1[j]=(Math.Pow(number[j],n))%n;
        Response.Write(c1[j]);
    }
 
    for (j = 0; j<i;>    
    {
        unicode1[j]=(Math.Pow(c1[j],d))%n;
        Response.Write("unicode1" + unicode1[j]);
    }
    double unicode1 = (int)(Math.Pow(c1,d)) % n;
    
    for (j = 0; j<i;>    
    {
        string str = char.ConvertFromUtf32((int)unicode1[j]);
        Response.Write(str);
    }
    string str = char.ConvertFromUtf32((int)unicode);

    Response.Write(str);

}