Insert the escape sequence "
textBox1.Text = "She said, "You deserve a treat!" ";
Insert the ASCII or Unicode character
textBox1.Text = "She said, " + 'u0022' + "You deserve a treat!" + 'u0022';
Define a constant for the character
const string quote = """;
textBox1.Text = "She said, " + quote + "You deserve a treat!"+ quote ;