Simple random Namegen

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 Random_name_generator_BASIC
{
    public partial class RNGB : Form
    {
        public RNGB()
        {
            InitializeComponent();
        }
        Random R = new Random();
        string RandomLetter = "abcdefghihjlmnopqrstuvwxyz";
        string RandomVovel = "aeiou";
        string RandomConsonant = "bcdfghjklmnpqrstvxyz";
        int Vovel; // How many letters have been vovels after each other?
        int Consonant; // Same as above but with consonants
        bool First = true;

        bool IsVovel(char Info) // Adds +1 to vovel if it is a vovel, or +1 to con.. if it is a con..
        {
            for (int I = 5; I >= 0; I--)
            {
                if (Info == RandomVovel[I])
                {
                    return true;
                }
            }
            return false;
        }

        char Letter() // Generate a raondom letter with some set logic
        {
            string LetterType = "";
            char Letter = "A"[0];

            if (First == true && CbControl.Checked == true && TbLetter.TextLength == 1)
            {
                try
                {
                    Letter = TbLetter.Text[0];
                }
                catch (FormatException)
                {
                    Letter = "A"[0];
                }
            }
            else
            {
                if (First == true)
                {
                    LetterType = RandomLetter;
                }
                else // code for making max two consonants or vovels appearing after each other.
                {
                    int I = R.Next(1, 100);

                    if (Consonant == 2)
                        LetterType = RandomVovel;
                    else if (Vovel == 2)
                        LetterType = RandomConsonant;
                    else if (Vovel == 1)
                    {
                        if (I > 70) // Makes sure there are a 70% chance of there being only one vovel
                            LetterType = RandomVovel;
                        else
                            LetterType = RandomConsonant;
                    }
                    else
                    {
                        if (I > 70) // Makes sure there are a 70% chance of there being only one consonant
                            LetterType = RandomConsonant;
                        else
                            LetterType = RandomVovel;
                    }
                }

                Letter = LetterType[R.Next(0, LetterType.Length)]; // Set a letter to a random part of the string LetterType
            }
            bool V = IsVovel(Letter); // Checks if Letter is a 'vovel' or notvovel

            if (V)
            {
                Vovel++;
                Consonant = 0;
            }
            else
            {
                Consonant++;
                Vovel = 0;
            }

            if (First)
            {
                First = false;
                return char.ToUpper(Letter);
            }
            else
                return Letter;
        }
        private void BActivate_Click(object sender, EventArgs e)
        {
            string Text = "";
            lblText.Text = "";
            int lenght = 3;

            if (CbLenght.Checked)
                lenght = (int)NUDLenght.Value;

            for (int I = (int)NumUD.Value; I > 0; I-- )
            {
                if (!CbLenght.Checked)
                    lenght = R.Next(3, 8);

                for (int Wordlenght = lenght;  Wordlenght > 0; Wordlenght--)
                {
                    Text += Letter();
                }

                lblText.Text += Text + "\n";
                Text = "";
                First = true;
            }
        }

        private void CbControl_CheckedChanged(object sender, EventArgs e)
        {
            if (CbControl.Checked)
                TbLetter.Visible = true;
            else
                TbLetter.Visible = false;
        }

        private void CbLenght_CheckedChanged(object sender, EventArgs e)
        {
            if (CbLenght.Checked)
                NUDLenght.Visible = true;
            else
                NUDLenght.Visible = false;
        }
    }
}