C＃错误中生成的文本框自动编号

Question

我正在用C＃创建一个简单的产品表单。虽然我生成了迄今为止我尝试过的自动编号错误，但我在下面附加了此内容。产品ID以00001开头。我在编写代码的方法内创建了方法Getproduct（）。错误显示语法错误。

public void Getproduct() {    
  string sql;
  SqlConnection con = new SqlConnection("server =.; initial catalog=product; integrated security=true");
  SqlDataAdapter dr;
  SqlDataReader dr1;
  sql = "SELECT id,product_name,product_desc,price FROM product Order By id Desc";
  SqlCommand com = new SqlCommand(sql, con);
  SqlDataReader dr = com.ExecuteReader();
  if (dr.Read() == true) {
    int id;
    int pid;
    id = (dr[0] + 1);
    pid = id.ToString("00000");
    else if IsDBNull(dr) {
      pid = ("00001");

    }

  }

}

Answer 1

尝试此代码

public void Getproduct()
    {
        string sql;
        SqlConnection con = new SqlConnection("server =.; initial catalog=product; integrated security=true");
        SqlDataAdapter dapt;
        SqlDataReader dr1;
        sql = "SELECT id,product_name,product_desc,price FROM product Order By id Desc";
        SqlCommand com = new SqlCommand(sql, con);
        SqlDataReader dr = com.ExecuteReader();

        int id;
        string pid;

        if (dr.Read() == true)
        {

            int val = 0;

            Int32.TryParse(dr[0].ToString(),out val);

            id = ( val + 1);
            pid = id.ToString("00000");
        }
        else if( Convert.IsDBNull(dr) )
            {
                pid = ("00001");

            }

        }