Encriptación al siguiente carácter ASCII

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace numero1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
//Variables
string f1, f2 = "", c;
int i, p;

private void button3_Click(object sender, EventArgs e)
{
Application.Exit();
}

//Entrada

private void textBox1_TextChanged(object sender, EventArgs e)
{
f1 = entrada.Text;
}

//Proceso



private void button1_Click(object sender, EventArgs e)
{
p = 0;
f1 = f1.Trim();
for (i = 0; i < f1.Length; i++)
{
c = f1.Substring(i, 1);
if (!c.Equals(" "))
{
c = char.ConvertFromUtf32(char.ConvertToUtf32(c, 0) + 1);
}
f2 += c;

//Salida

salida.Text = f2;
}
}
}
}