使用 int64 值格式化字符串

Question

i have a web service in which training number is assigning as per my database

there is a line

dates + "1"; this lines add 1 in date

like 27012017 will become 270120171

then i convert this into int64

newid = Convert.ToInt64(dates);

but now i want to add trainer id in this

so i updated my line with this

dates ="00"+trainerid +"-"+ dates + "1";
newid = Convert.ToInt64(dates);

the error is coming input string is not in correct format,

i know this is because of the addition of +"-"+

but i want to store the data in this format only

and my whole portion look like

DateTime dt = DateTime.Now;
string dates = dt.ToString();
dates = dates.Replace("-", "");
dates = dates.Substring(0, 8);
        SqlCommand cmdbill = new SqlCommand("select top 1 * from listmybill where bill_id like @trid order by bill_id desc", con);
        con.Open();
        cmdbill.Parameters.AddWithValue("@trid", "%" + dates + "%");
        SqlDataReader dr = cmdbill.ExecuteReader();
        while (dr.Read())
        {
            value = dr["bill_id"].ToString();
        }

        con.Close();
        con.Open();
        SqlDataAdapter da = new SqlDataAdapter(cmdbill);
        DataTable dat = new DataTable();
        da.Fill(dat);
        if (dat.Rows.Count > 0)
        {
            newid = Convert.ToInt64(value);
            newid = newid + 1;
        }
        else
        {
            dates ="00"+trainerid +"-"+ dates + "1";
            newid = Convert.ToInt64(dates);
        }
        con.Close();

what should i do here,

i want to enter the data like 001-270120171 and if i convert toInt64 into string,

there can be problem when a row found in the table

if (dat.Rows.Count > 0) 
{
    newid = Convert.ToInt64(value);
    newid = newid + 1; 
}

what i need to do now?

i want to store this into my database

Answer 1

I hardly think you will be doing mathematical calculations on this training number string. I suggest that you convert the int in your database into a varchar using alter statement. Then you you will be able to store the training number in whichever format you like.

Answer 2

You can change new id to string and do the following

if (dat.Rows.Count > 0) 
{
    newid = Convert.ToString(Convert.ToInt64(value)+1);
}
 else
{
   newid="00"+trainerid +"-"+ dates + "1";

}