convert multiline text box value into byte

[abdulhussain]

protected void btnUpload_Click(object sender, EventArgs e){
 string pic = ASCIIEncoding.ASCII.GetString(fileUpload1.FileBytes);
 TextBox1.Text = value.ToString();

//Here i get pic[40385]
//The value in the textbox is just like: ????�JFIF��`�`� �??FExif��MM�*� ���Q�
}

protected void btnsave_Click(object sender, EventArgs e){
pic = Encoding.ASCII.GetBytes(TextBox1.Text.ToString().TrimEnd());
//Here i get pic[40685]
//In save button event i convert that textbox value into byte but i get wrong size(pic[40685])
}

On two different event i get two different value which cause file not open due to file corrupted

[abdulhussain]

FF-D8-FF-E0-00-10-4A-46-49-46-00-01-01-01-00-60-00-60

how to convert this value into byte array