Why the form hang at inputs focus ?

hi,
i have xtraform (to manage Branch ) that contains some inputs and gridview.
after loading the form , i can focus any input (ex:- CodeInput.Text )without any problems. but when i click EditGridbtnREP , the inputs filled with the data.

please Note: there are a relation between ad_branches table and many others tables.

when i focus any inputs again , the form hang , and take 2-3 min. to respond.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
using DevExpress.XtraEditors;
using DevExpress.XtraSplashScreen;
using MrSales.MrSLanguages;
using MrSales.MrSModels;
using System.Data.Entity;
using System.Runtime.InteropServices;

namespace MrSales.MrSViews.CompanyConfig
{
    public partial class ManageBranches : DevExpress.XtraEditors.XtraForm
    {
        public int ID = 0;
        public ManageBranches()
        {

            SplashScreenManager.CloseForm(false);

            SplashScreenManager.ShowForm(this, typeof(waitForm), true, true, false);
            try { SplashScreenManager.Default.SetWaitFormDescription(strings.Creating_basic_components); } catch { }


            InitializeComponent();


            mrsalesdbEntities dbContext = ConnectionTools.OpenConn();
            try{ SplashScreenManager.Default.SetWaitFormDescription(strings.loading_branches_list); } catch { }
            ad_branchesBindingSource.DataSource = dbContext.ad_branches.ToList();   


            try { SplashScreenManager.Default.SetWaitFormDescription(strings.LOADING_company_data); } catch { }
            ad_company_dataBindingSource.DataSource = dbContext.ad_company_data.Local.ToBindingList();


            try { SplashScreenManager.Default.SetWaitFormDescription(strings.loading_Countries_Cities); } catch { }
            ad_countryBindingSource.DataSource = dbContext.ad_country.ToList();
            ad_cityBindingSource.DataSource = dbContext.ad_city.ToList();



        }
        //to drag form
        const int HT_CAPTION = 0x2;
        const int WM_NCLBUTTONDOWN = 0xA1;

        [DllImportAttribute("user32.dll")]
        public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
        [DllImportAttribute("user32.dll")]
        public static extern bool ReleaseCapture();



        private void ManageBranches_Load(object sender, EventArgs e)
        {
            
            SplashScreenManager.Default.SetWaitFormDescription(strings.loading_interface);

            //Func to Load All Basic And Requires Design Varibles 
            MrSControls.FormLoad.PublicDesign(this);
            CompanyInput.EditValue = 1;

            SplashScreenManager.CloseForm(false); 
        }

        private void CloseFrmBtn_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void HeaderPanel_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                ReleaseCapture();
                SendMessage(Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0);
            }
        }

        private void EditGridbtnREP_ButtonClick(object sender, DevExpress.XtraEditors.Controls.ButtonPressedEventArgs e)
        {

            ID = Convert.ToInt32(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_ID"));
            CompanyInput.EditValue = Convert.ToInt32(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "comp_ID"));
            CodeInput.Text = Convert.ToString(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Code"));
            NameInput.Text = Convert.ToString(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Name"));
            StatusToggle.EditValue = Convert.ToInt32(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Status")) == 0 ? false : true;
            Mobile1Input.Text = Convert.ToString(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Mobile1"));
            Mobile2Input.Text = Convert.ToString(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Mobile2"));
            Mobile3Input.Text = Convert.ToString(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Mobile3"));
            PhoneInput.Text = Convert.ToString(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Phone"));
            AddressInput.Text = Convert.ToString(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "branche_Address"));
            CountryInput.EditValue = Convert.ToInt32(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "Country"));
            CityInput.EditValue = Convert.ToInt32(gridView1.GetRowCellValue(gridView1.FocusedRowHandle, "City"));
        }
    }
}

What I have tried:

i created new form and copied the controls one by one and the problem still exist

i tried comment the codes one by one but the same issue

SplashScreenManager.CloseForm(false);

           SplashScreenManager.ShowForm(this, typeof(waitForm), true, true, false);
           try { SplashScreenManager.Default.SetWaitFormDescription(strings.Creating_basic_components); } catch { }


           InitializeComponent();


           mrsalesdbEntities dbContext = ConnectionTools.OpenConn();
           try{ SplashScreenManager.Default.SetWaitFormDescription(strings.loading_branches_list); } catch { }
           ad_branchesBindingSource.DataSource = dbContext.ad_branches.ToList();


           try { SplashScreenManager.Default.SetWaitFormDescription(strings.LOADING_company_data); } catch { }
           ad_company_dataBindingSource.DataSource = dbContext.ad_company_data.Local.ToBindingList();


           try { SplashScreenManager.Default.SetWaitFormDescription(strings.loading_Countries_Cities); } catch { }
           ad_countryBindingSource.DataSource = dbContext.ad_country.ToList();
           ad_cityBindingSource.DataSource = dbContext.ad_city.ToList();

Tags: C#, Entity Framework, DevExpress