ComboBox SelectedItem属性不会更改

Question

Hi I've got a problem with a comboBox.
At the beginning the documentTypeComboBox.SelectedItem value is null, then the GetDataRow() method return DataRow which is not null (100% sure that it return not null value for my test)
After all the value of the SelectedItem property is still null. No idea what is wrong. I'm 100% sure that the returned DataRow is assigned as comboBox DataSource row

    public void SetDefaultData()
    {
        documentTypeComboBox.SelectedItem = null;

        dataWystawieniaDate.Value = _Faktura.DataWystawienia;
        dataSprzedazyDate.Value = _Faktura.DataSprzedazy;

        warehouseComboBox.SelectedItem = Helpers.GetDataRow(_Dictionary.Magazines, _Faktura.Magnum);
        paymentMethodComboBox.SelectedItem = Helpers.GetDataRow(_Dictionary.SpPaymentMethodsData, _Faktura.IdSposobuPlatnosci);
        priceComboBox.SelectedItem = Helpers.GetDataRow(_Dictionary.PricesData, _Faktura.RodzajCeny);
        discountComboBox.SelectedItem = Helpers.GetDataRow(_Dictionary.RabatyData, _Faktura.RodzajRabatu);
        documentTypeComboBox.SelectedItem = Helpers.GetDataRow(_Dictionary.SpDocumentsCodes, _Faktura.Kod, documentTypeComboBox.DisplayMember);

        documentNumberTextBox.Text = _Faktura.Numer;
        kwotaBruttoTextBox.Text = _Faktura.PlnWartoscBrutto.ToString();
    }


    public static DataRow GetDataRow(DataTable dt, string value, string fieldName)
    {
        foreach (DataRow dr in dt.Rows)
        {
            if (dr[fieldName].ToString() == value)
                return dr;
        }
        return null;
    }

Answer 1

I think i figure it out. SelectedItem property is DataRowView not DataRow. This explains why it doesn't select the correct value. Use SelectedValue instead :)

https://social.msdn.microsoft.com/Forums/windows/en-us/77b23eb9-112f-4fea-9d3a-486b822f22ea/combobox-datatable-selecteditem