Visual C# code assistance?

here is my code below, on my form I have 3 textboxes and a button, what is the code to convert the value entered in a textbox to an integer, here is my error





quantity = (int)(txtQuantity.Text);





int quantity;


decimal unitPrice;


decimal totalPrice;





quantity = (int)(txtQuantity.Text);





// The price of one CD will depend on the number ordered


// The more the customer orders, the lower value for each


if (quantity %26lt; 20)


{


unitPrice = 20;


if (quantity %26lt; 50)


{


unitPrice = 15;


}


if (quantity %26lt; 100)


{


unitPrice = 12;


}


if (quantity %26lt; 500)


{


unitPrice = 8;


}


}


else


{


unitPrice = 5;


}


tota

Visual C# code assistance?
int quantity = Int32.Parse(txtQuantity.Text);