IF condition is not working

Abrar how AND opertor work AND if all the condition are true then it give true if any one of them is flase then it give false. 
The condition is If AppointmentNumber or PatientID or AppointmentID is exist then it shows record already exist here.

debug your code by adding break point and check your conditions

Hi Instead of OR cluase you have to check AND clause in the exits, try below code

private void btnAdd_Click(object sender, EventArgs e)
        {
            if (txtAppointmentID.Text.Length > 0 && txtAppointmentNumber.Text.Length > 0 && txtPatientID.Text.Length > 0 && txtDoctorName.Text.Length > 0 && DateTimeAppointment.Text.Length > 0 && txtAppointmentDuration.Text.Length > 0 && txtAppointmentCharges.Text.Length > 0)
                if (Appointment.IsExist(txtAppointmentID.Text) && Appointment.IsExist(txtAppointmentNumber.Text) && Appointment.ISExit(txtPatientID.Text) && Appointment.ISExit(DateTimeAppointment.Text))
                {
                    MessageBox.Show("Appointment already Exist");
                }
                else
                {
                    if (Appointment.InsertAppointmentRecord(txtAppointmentID.Text , txtAppointmentNumber.Text, txtPatientID.Text, txtDoctorName.Text, DateTimeAppointment.Value, txtAppointmentDuration.Text, txtAppointmentCharges.Text))
                    {
                        MessageBox.Show("Appointment Record Inserted Successfully" , "Insertion Succeeded");
                        GetAppointmentTable();

                    }
                    else
                    {
                        MessageBox.Show("Appointment Record Insertion Failed" , "Insertion Failed");
                    }
                }
            else
            {
                MessageBox.Show( "Fill Required Field" , "Empty Fields");
        }
        }