Item collection cannot be modified when datasource is set

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C#

WinForms

this is c# winform and im using tabControl.
whenever the tabPage is loaded, the code will read the ID/data from sql and add them into the combobox:

private void tpProduct_Enter(object sender, EventArgs e)
       {
           MySql.Data.MySqlClient.MySqlDataReader dr = runQuery("SELECT * FROM category");

           this.combBox1.Items.Clear();

           var dict = new Dictionary<string, string>();
           while (dr.Read())
           {
               dict.Add(dr["id"].ToString(), dr["name"].ToString());
           }
           combBox1.DataSource = new BindingSource(dict, null);
           combBox1.DisplayMember = "Value";
           combBox1.ValueMember = "Key";

           ConnectionClose();
       }

if i switch between the tab too fast, then this error message pop up "Item collection cannot be modified when datasource is set"

any idea how to solve this?