Unable to encode a querystring in url.

URLEncode converts Spaces ( ) to plus signs (+) and Non-alphanumeric characters to their hexadecimal representation. It will not convert string.

You can use the below encoding mechanism to convert to different format.

public string fnEncode(string str)
{
	byte[] byteEncode = new byte[str.Length + 1];
	string strEncoded = null;

	byteEncode = System.Text.Encoding.UTF8.GetBytes(str);
	strEncoded = Convert.ToBase64String(byteEncode);

	return strEncoded;
}

and call this.

Response.Redirect("WebForm2.Aspx?Parameter=" + fnEncode(txtName.Text));

For Decode:

public string fnBase64Decode(string strPwd)
{
	System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();
	System.Text.Decoder utf8Decode = null;
	byte[] byteDecode = null;
	int intCharCnt = 0;
	string strDecoded = null;

	utf8Decode = encoder.GetDecoder();
	byteDecode = Convert.FromBase64String(strPwd);
	intCharCnt = utf8Decode.GetCharCount(byteDecode, 0, byteDecode.Length);

	char[] charDecoded = new char[intCharCnt + 1];

	utf8Decode.GetChars(byteDecode, 0, byteDecode.Length, charDecoded, 0);
	strDecoded = new string(charDecoded);

	return strDecoded;
}

use this

public static string Encrypt(string toEncrypt, string key, bool useHashing)
    {
        byte[] keyArray;
        byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

        if (useHashing)
        {
            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
            keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
        }
        else
            keyArray = UTF8Encoding.UTF8.GetBytes(key);

        TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
        tdes.Key = keyArray;
        tdes.Mode = CipherMode.ECB;
        tdes.Padding = PaddingMode.PKCS7;

        ICryptoTransform cTransform = tdes.CreateEncryptor();
        byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

        return Convert.ToBase64String(resultArray, 0, resultArray.Length).Replace("+"," ");
    }


    public static string Decrypt(string toDecrypt, string key, bool useHashing)
    {
        toDecrypt = toDecrypt.Replace(" ", "+");
        byte[] keyArray;
        byte[] toEncryptArray = Convert.FromBase64String(toDecrypt);

        if (useHashing)
        {
            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
            keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
        }
        else
            keyArray = UTF8Encoding.UTF8.GetBytes(key);

        TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
        tdes.Key = keyArray;
        tdes.Mode = CipherMode.ECB;
        tdes.Padding = PaddingMode.PKCS7;

        ICryptoTransform cTransform = tdes.CreateDecryptor();
        byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

        return UTF8Encoding.UTF8.GetString(resultArray);
    }

While calling use the syntax

string Id = Decrypt(ID.ToString().Replace("$", "/").Replace(" ", "+"), "Test", true);
string Test = Encrypt(pass.ToString(), "Test", true);