Question

我遇到了有关标记重复数据的问题。在我的项目中，已经存在的记录不能记录两次。我关注了stackoverflow的多篇文章，并且知道我必须使用 executescalar 来执行此操作。.我使用了executescalar，但它无法处理现有数据。您能帮我解决一下吗？

这是我的代码部分：

    {

        appointmentdate = dtappointmentdate.Value;
        today = DateTime.Now;
        String prob = txtproblemdefination.Text;
        String rec = "";
        if (appointmentdate < today)
        {
            MessageBox.Show("Please Enter Correct Date.");
        }
        else
        {
            SqlCommand check_User_Name = new SqlCommand("SELECT count(*) FROM appointmentTable WHERE PatientName = '" + patientname + "'And (DoctorName = '" + docname + "'And AppointmentDateSet = '" + appointmentdate + "')", sqlCon);
            check_User_Name.Parameters.AddWithValue("@patname", patientname);
            check_User_Name.Parameters.AddWithValue("@docname", docname);
            check_User_Name.Parameters.AddWithValue("@appointmentdate", appointmentdate);
            if (sqlCon.State != ConnectionState.Open)
            {
                sqlCon.Open();
            }
            int UserExist = (Int32)check_User_Name.ExecuteScalar();

            if (UserExist > 0)
            {
                MessageBox.Show("You can't make appointment twice a day. ");
            }

            else
            {
                SqlCommand insertCommand = new SqlCommand("insert into appointmentTable(PatientName,DoctorName,ClinicLocation,AppointmentDateSet,Problem,Recommendation) values(@docname, @patname, @doclocation, @appointmentdate,@prob,@rec)");
                insertCommand.Parameters.AddWithValue("@patname", patientname);
                insertCommand.Parameters.AddWithValue("@docname", docname);
                insertCommand.Parameters.AddWithValue("@doclocation", doclocation);
                insertCommand.Parameters.AddWithValue("@appointmentdate", appointmentdate);
                insertCommand.Parameters.AddWithValue("@prob", prob);
                insertCommand.Parameters.AddWithValue("@rec", rec);
                int row = objdbaccess.executeQuery(insertCommand);
                if (row == 1)
                {
                    MessageBox.Show("Appointment is Successfully Done.");
                }
                else
                {
                    MessageBox.Show("Error!Please try again later.");
                }
                sqlCon.Close();
            }

        }

Answer 1

您应该将代码更改为：

我假设约会日期的类型为DateTime，否则您可以从here中选择正确的类型

using(var check_User_Name= SqlCommand("SELECT count(*) FROM appointmentTable WHERE PatientName = @patname And DoctorName = @docname And AppointmentDateSet = @appointmentdate )", sqlCon)
{

    check_User_Name.Parameters.Add("@patname", DbType.String).Value = patientname;
    check_User_Name.Parameters.Add("@docname", DbType.String).Value = docname;
    check_User_Name.Parameters.Add("@appointmentdate", DbType.DateTime).Value = appointmentdate;        
    con.Open();
    int UserExist = (int)check_User_Name.ExecuteScalar();
    // Followed by your code
}

执行标量无法返回现有行

1 个答案: