How i display data in combobox using another combobox in c# winapp

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C#

I have two table ,
first table Like this :- city_id , City_Name .... city_id is PK
------ , ---------
1 , city1
2 , city2

table 2 : - City_id , center_id , Center_Name ..... City_id is FK, Center_id is PK
-------- , ---------- , -----------
1 , 1 , center1
1 , 2 , center2
2 , 3 , center3
2 , 4 , center4

i have two combobox ,the first to display City_Name ,the second to dispaly center_Name when the user choose City_NAme fro first combobox .

this is my code :-

void FillComboCity()
        {          
            try
            {
                dSet = new DataSet();
                con.Open();
                s = "select City_id , City_Name from City";
                sCommand = new SqlCommand(s, con);
                sdAdapter = new SqlDataAdapter();
                sdAdapter.SelectCommand = sCommand;
                sdAdapter.Fill(dSet);
                DataRow dr = dSet.Tables[0].NewRow();
                dr.ItemArray = new object[2] { 0, " ---Select--- " };
                dSet.Tables[0].Rows.InsertAt(dr, 0);
                CB_City.ValueMember = "City_id";
                CB_City.DisplayMember = "City_Name";
                CB_City.DataSource = dSet.Tables[0];
                con.Close();
            }
            catch
            {
                return;
            }
        }

        void FillComboCenter()
        {
            try
            {
                dSet = new DataSet();
                con.Open();
                s = "select Center_id , Center_Name from Center where City_id = '"+CB_City.Text+"'";
                sCommand = new SqlCommand(s, con);
                sdAdapter = new SqlDataAdapter();
                sdAdapter.SelectCommand = sCommand;
                sdAdapter.Fill(dSet);
                DataRow dr = dSet.Tables[0].NewRow();
                dr.ItemArray = new object[2] { 0, " ---Select--- " };
                dSet.Tables[0].Rows.InsertAt(dr, 0);
                CB_Center.ValueMember = "Center_id";
                CB_Center.DisplayMember = "Center_Name";
                CB_Center.DataSource = dSet.Tables[0];
                con.Close();
            }
            catch
            {
                return;
            }
        }
 private void FRM_PatientData_Load(object sender, EventArgs e)
        {
            
                FillComboCity();
                FillComboCenter(); 
        }

What I have tried:

How i display data in combobox?