C# SQL hatası

SqlCommand komut3 = new SqlCommand("Select DoktorAd,DoktorSoyad From Tbl_Doktorlar where DoktorBrans = @p1", bgl.baglanti());
 komut3.Parameters.AddWithValue("@p1", CmbBrans.Text);
 SqlDataReader dr3 = komut3.ExecuteReader();
 while (dr3.Read())
 {
 CmbDoktor.Items.Add(dr3[0] + " " + dr3[1]);
 }
 bgl.baglanti() .Close();

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 Proje_Hastane
{
    public partial class FrmHastaDetay : Form
    {
        public FrmHastaDetay()
        {
            InitializeComponent();
        }

        public string tc;

        sqlbaglantisi bgl = new sqlbaglantisi();

        private void FrmHastaDetay_Load(object sender, EventArgs e)
        {
            LblTC.Text = tc;

            //Ad Soyad Çekme
            SqlCommand komut = new SqlCommand("Select Hastaad,HastaSoyad from Tbl_Hastalar where Hastatc = @a1", bgl.baglanti());
            komut.Parameters.AddWithValue("@a1", LblTC.Text);
            SqlDataReader dr = komut.ExecuteReader();
            while (dr.Read())
            {
                LblAdSoyad.Text = dr[0] + " " + dr[1];
            }
            bgl.baglanti().Close();

            //Randevu Geçmişi
            DataTable dt = new DataTable();
            SqlDataAdapter da = new SqlDataAdapter("Select * From Tbl_Randevular where HastaTC = " + tc, bgl.baglanti());
            da.Fill(dt);
            dataGridView1.DataSource = dt;

            //Branşları Çekme
            SqlCommand komut2 = new SqlCommand("Select BransAd from Tbl_Branslar", bgl.baglanti());
            SqlDataReader dr2 = komut2.ExecuteReader();
            while (dr2.Read())
            {
                CmbBrans.Items.Add(dr2[0]);
            }
            bgl.baglanti().Close();
        }

        private void CmbDoktor_SelectedIndexChanged(object sender, EventArgs e)
        {
            DataTable dt = new DataTable();
            SqlDataAdapter da = new SqlDataAdapter("Select * From Tbl_Randevular where RandevuBrans ='" + CmbBrans.Text + "'", bgl.baglanti());
            da.Fill(dt);
            dataGridView1 .DataSource = dt;


        }

        private void CmbBrans_SelectedIndexChanged(object sender, EventArgs e)
        {
            SqlCommand komut3 = new SqlCommand("Select DoktorAd,DoktorSoyad From Tbl_Doktorlar where DoktorBrans = @p1", bgl.baglanti());
            komut3.Parameters.AddWithValue("@p1", CmbBrans.Text);
            SqlDataReader dr3 = komut3.ExecuteReader();
            while (dr3.Read())
            {
                CmbDoktor.Items.Add(dr3[0] + " " + dr3[1]);
            }
            bgl.baglanti() .Close();

        }

        private void CmbDoktor_SelectedIndexChanged_1(object sender, EventArgs e)
        {
            
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;

namespace Proje_Hastane.
{
 internal class sqlbaglantisi.
 {
 public SqlConnection baglanti()
 {
 SqlConnection baglan = new SqlConnection("Data Source=DESKTOP-SLPRUK2;Initial Catalog=HastaneProje;Integrated Security=True");
 baglan.Open();
 return baglan;
 }
 }
}

try
{
  // KODLARINIZ
}
catch (Exception e)
{
  Console.WriteLine(e.Message); // Hata çıktısı
}