Question

I have a table called Product(the ProductCode field data type is varchar ):

ID     ProductName    ProductCode
1       aaa              0001
2       bbb              0002
3       ccc              0004
4       ddd              0006
5       eee              0007
6       fff              0008

My problem is : IF current the ProductCode field value is ‘0006’.I would like to generate
a value that is ‘0009’ .

public string GenerateNumber(string codeNumber)
{

    StringBuilder strSql = new StringBuilder();
    strSql.Append("select count(1) from Product");
    strSql.Append(" where ProductCode=@codeNumber");
    SqlParameter[] parameters = {
        new SqlParameter("@codeNumber", SqlDbType.NChar,8)
    };
    parameters[0].Value = codeNumber;
    bool existInDatabase = SQLHelper.Exists(strSql.ToString(), parameters);
    if (existInDatabase)
    {
        this.GenerateNumber((Convert.ToInt32(codeNumber) + 1).ToString().PadLeft(4, '0'));
    }
    return (Convert.ToInt32(codeNumber) + 1).ToString().PadLeft(4, '0');
}

Call this function some thing like :GenerateNumber(“0006”)

The result shuold return 0009 ,but is not !

Can anyone help me out ?Thanks ,I am a newbie!

Answer 1

Using recursion in asp.net for this seems like too much of an overhead.

You could do this best by writing a stored procedure to GenerateNextProductCode that used a common table expression to generate this value.

The reason this code is failing is you are not returning the result of your recursion.

Correct it like this:

public string GenerateNumber(string codeNumber)
{

        StringBuilder strSql = new StringBuilder();
        strSql.Append("select count(1) from Product");
        strSql.Append(" where ProductCode=@codeNumber");
        SqlParameter[] parameters = {
                new SqlParameter("@codeNumber", SqlDbType.NChar,8)
        };
        parameters[0].Value = codeNumber;
        bool existInDatabase = SQLHelper.Exists(strSql.ToString(), parameters);
        if (existInDatabase)
        {
           return this.GenerateNumber((Convert.ToInt32(codeNumber) + 1).ToString().PadLeft(4, '0'));
        }
        return (Convert.ToInt32(codeNumber) + 1).ToString().PadLeft(4, '0');
}