How to generate automatic bill number from database in c#

This is just a method which will return new bill no. then you can pass that to your form.
or you can mark this method as static 
so you can use TextBox1.Text=GenerateNumber(your_Max_bill_no);

Hi Dear,
find the method to generate number in sequence. I am using the silar pattern in one of my project.

public string GenerateNumber(string ReceivedId)
        {
            // OR0000  // pattern
            if (string.IsNullOrEmpty(ReceivedId))
            {
                ReceivedId = "BILL_000001";
            }
            string nextId = string.Empty;
            int len = ReceivedId.Length;
            string splitNo = ReceivedId.Substring(5, len - 5);//This line will ignore the string values and read only the numeric values
            int num = Convert.ToInt32(splitNo);
            num++;// Increment the numeric value
            nextId = ReceivedId.Substring(0, 5) + num.ToString("000000");//Concatenate the string value and the numeric value after the increment
            return nextId;
           // return null;
        }

in input parameter use MAX(YOUR_DB_FIELD) .