Please help me in steganography

public void encryption()
{
      var originalbmp = new Bitmap(Bitmap.FromFile("../../OriginalImage.png")); //Actual image used to encrypt the message
           
      var encryptbmp = new Bitmap(originalbmp.Width, originalbmp.Height); // To hold the encrypted image  

var originalText="My message to encrypr"; 
var ascii = new List<int>(); // To store individual value of the pixels 
      foreach (char character in originalText)
      {
             int asciiValue = Convert.ToInt16(character); // Convert the character to ASCII
             var firstDigit = asciiValue / 1000; // Extract the first digit of the ASCII
             var secondDigit = (asciiValue - (firstDigit * 1000)) / 100; //Extract the second digit of the ASCII
             var thirdDigit = (asciiValue - ((firstDigit * 1000) + (secondDigit * 100)))/10;//Extract the third digit of the ASCII
             var fourthDigit = (asciiValue - ((firstDigit * 1000) + (secondDigit * 100)+(thirdDigit * 10))); //Extract the third digit of the ASCII
             ascii.Add(firstDigit); // Add the first digit of the ASCII
             ascii.Add(secondDigit); // Add the second digit of the ASCII
             ascii.Add(thirdDigit); // Add the third digit of the ASCII
             ascii.Add(fourthDigit ); // Add the fourth digit of the ASCII
     }
     var count = 0; // Have a count
     for (int row = 0; row < originalbmp.Width; row++) // Indicates row number
     {
           for (int column = 0; column < originalbmp.Height; column++) // Indicate column number
           {
                 var color = originalbmp.GetPixel(row, column); // Get the pixel from each and every row and column
                 encryptbmp.SetPixel(row, column, Color.FromArgb(color.A -((count < ascii .Count ) ? ascii[count]:0), color)); // Set ascii value in A of the pixel
           }
    }
    encryptbmp.Save("../../EncryptedImage.png", ImageFormat.Png); // Save the encrypted image   
}

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private void decryption()
{
     var characterValue = 0; // Have a variable to store the ASCII value of the character
     string encryptedText = string.Empty; // Have a variable to store the encrypted text
     var ascii = new List<int>(); // Have a collection to store the collection of ASCII
     var encryptbmp = new Bitmap(Bitmap.FromFile("../../EncryptedImage.png")); // Load the transparent image
 
     for (int row = 0; row < encryptbmp.Width; row++) // Indicates row number
     {
           for (int column = 0; column < encryptbmp.Height; column++) // Indicate column number
           {
                var color = encryptbmp.GetPixel(row, column); // Get the pixel from each and every row and column
                 ascii.Add(255 - color.A); // Get the ascii value from A value since 255 is default value
           }
    }
    for (int i = 0; i < ascii.Count; i++)
    {
          characterValue = 0;
          characterValue += ascii[i] * 1000; // Get the first digit of the ASCII value of the encrypted character
          i++;
          characterValue += ascii[i] * 100; // Get the second digit of the ASCII value of the encrypted character
          i++;
          characterValue += ascii[i] * 10;  // Get the first third digit of the ASCII value of the encrypted character
          i++;
          characterValue += ascii[i]; // Get the first fourth digit of the ASCII value of the encrypted character
          if (characterValue != 0)
             encryptedText += char.ConvertFromUtf32(characterValue); // Convert the ASCII characterValue into character
          }
          MessageBox.Show(encryptedText); // Showing the encrypted message in message box
}