C# Warning for non-exist user ID

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C#

Hello,

I have a C# Windows form Project with SQL Server. I have a ticket opening form. At this form, user opens a ticket for help desk. What I want to do is, while user opening a ticket, there must be a warning for cases non-exist users, at this case the ticket must be prevented. For example, I want to open a ticket and I enter 21 for kullaniciID, but this ID does not exist at my user table and this record must be prevented, of course with a message. How can I do that?

Thanks for your help. My code block is below:

	using System;
	using System.Collections.Generic;
	using System.ComponentModel;
	using System.Data;
	using System.Drawing;
	using System.Linq;
	using System.Text;
	using System.Threading.Tasks;
	using System.Windows.Forms;
	using System.Data.SqlClient;
	
	namespace ITHelpDeskProject
	{
	    public partial class CgrKydOlstr : Form
	    {
	        public CgrKydOlstr()
	        {
	            InitializeComponent();
	        }
	
	        private void CgrKydOlstr_Load(object sender, EventArgs e)
	        {
	            CMBBOXproblemTur.Items.Add("Donanım Arızası");
	            CMBBOXproblemTur.Items.Add("Yazılım Problemi");
	            CMBBOXproblemTur.Items.Add("Network Problemi");
	        }
	
	        private void BTNkaydet_Click(object sender, EventArgs e)
	        {
	            SqlConnection baglanti = new SqlConnection("Data Source=EMREY\\MS_SQLSERVER;Initial Catalog=ITHelpDeskProjesi;Integrated Security=True");
	            baglanti.Open();
	
	            string SonKayitID;
	
	            DateTime dt = Convert.ToDateTime(DTPCKRkayitTarih.Value.ToString("yyyy-MM-dd"));
	            String zaman = dt.ToString("yyyy-MM-dd hh:mm:ss");
	
	            SqlCommand cmd = new SqlCommand("INSERT INTO tblKayit(kullaniciID, bilgisayarID, yaziciID, problemTur, kayitTarihi) VALUES(@kullaniciID, @bilgisayarID, @yaziciID, @problemTur, @kayitTarihi); select scope_identity()");
	
	            cmd.Parameters.AddWithValue("@kullaniciID", TXTBOXkulID.Text);
	            cmd.Parameters.AddWithValue("@bilgisayarID", TXTBOXbilID.Text);
	            cmd.Parameters.AddWithValue("@yaziciID", TXTBOXyaziciID.Text);
	            cmd.Parameters.AddWithValue("@problemTur", CMBBOXproblemTur.Text);
	            cmd.Parameters.AddWithValue("@kayitTarihi", dt);
	
	            cmd.Connection = baglanti;
	
	            SonKayitID = cmd.ExecuteScalar().ToString();
	
	            MessageBox.Show("Yardım masası çağrı kaydınız oluşturulmuştur. Çağrı kaydınız hakkında bilgi almak için kullanabileceğiniz referans numaranız : " + SonKayitID);
	
	            baglanti.Close();
	            CgrKydOlstr_Load(sender, e);
	
	        }
	
	        private void BTNanaSayfa_Click(object sender, EventArgs e)
	        {
	            personelAnaMenu prsana = new personelAnaMenu();
	            prsana.Show();
	            this.Hide();
	        }
	
	        private void BTNsistemdenCik_Click(object sender, EventArgs e)
	        {
	            this.Close();
	        }
	
	        private void CgrKydOlstr_FormClosing(object sender, FormClosingEventArgs e)
	        {
	            Application.Exit();
	        }
	
	    }
}

[edit]Code block added - OriginalGriff[/edit]