DevExpress ASPxComboBox SelectItem is null

Question

I have an ASPxComboBox which I was able to get filtering correctly on user input. Now I want to save the selected item to the database. But when I try to get the SelectedItem it is null.

ASP

<dxe:ASPxComboBox ID="cboInstructor" runat="server" Width="100%"
            EnableCallbackMode="True" CallbackPageSize="10"
            IncrementalFilteringMode="Contains" ValueType="System.Int32" ValueField="employee_id"
            OnItemsRequestedByFilterCondition="cboInstructor_OnItemsRequestedByFilterCondition_SQL"
            OnItemRequestedByValue="cboInstructor_OnItemRequestedByValue_SQL" TextFormatString="{0} {1}"
            DropDownStyle="DropDown"
        >
            <Columns>
                <dxe:ListBoxColumn FieldName="display_forename" Caption="Forename" />
                <dxe:ListBoxColumn FieldName="display_surname" Caption="Surname" />
            </Columns>
        </dxe:ASPxComboBox>

        <asp:SqlDataSource ID="SqlDataSourceInstruct" runat="server" ConnectionString="Server=testserver;User ID=root;Password=password;Persist Security Info=True;Database=central" ProviderName="MySql.Data.MySqlClient" SelectCommand="GetUser" SelectCommandType="StoredProcedure">
            <SelectParameters>
                <asp:Parameter Name="filter" Type="String" />
                <asp:Parameter Name="startIndex" Type="Int32" />
                <asp:Parameter Name="endIndex" Type="Int32" />
            </SelectParameters>
        </asp:SqlDataSource>
        <asp:SqlDataSource ID="SqlDataSourceInstructPopulate" runat="server" ConnectionString="Server=testserver;User ID=root;Password=password;Persist Security Info=True;Database=central" ProviderName="MySql.Data.MySqlClient" SelectCommand="GetUser" SelectCommandType="StoredProcedure">
        </asp:SqlDataSource>

        <asp:Button ID="btnTest" runat="server" Text="Test" OnClick="btnTest_Click" />

CS

    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void cboInstructor_OnItemsRequestedByFilterCondition_SQL(object source, ListEditItemsRequestedByFilterConditionEventArgs e)
    {
        ASPxComboBox comboBox = (ASPxComboBox)source;

        SqlDataSourceInstruct.SelectParameters.Clear();
        SqlDataSourceInstruct.SelectParameters.Add("filter", TypeCode.String, string.Format("%{0}%", e.Filter));
        SqlDataSourceInstruct.SelectParameters.Add("startIndex", TypeCode.Int32, (e.BeginIndex + 1).ToString());
        SqlDataSourceInstruct.SelectParameters.Add("endIndex", TypeCode.Int32, (e.EndIndex + 1).ToString());
        comboBox.DataSource = SqlDataSourceInstruct;
        comboBox.DataBind();
    }

    protected void cboInstructor_OnItemRequestedByValue_SQL(object source, ListEditItemRequestedByValueEventArgs e)
    {
        long value = 0;
        if (e.Value == null)
            return;
        if (!Int64.TryParse(e.Value.ToString(), out value))
            return;
        ASPxComboBox comboBox = (ASPxComboBox)source;
        SqlDataSourceInstructPopulate.SelectCommand = @"SELECT employee_id, display_surname, display_forename FROM user_record WHERE employee_id = @ID ORDER BY display_forename";
        SqlDataSourceInstructPopulate.SelectCommandType = System.Web.UI.WebControls.SqlDataSourceCommandType.Text;
        SqlDataSourceInstructPopulate.SelectParameters.Clear();
        SqlDataSourceInstructPopulate.SelectParameters.Add("ID", TypeCode.Int64, e.Value.ToString());
        comboBox.DataSource = SqlDataSourceInstructPopulate;
        comboBox.DataBind();
        comboBox.ValueField = "employee_id";
    }

    protected void btnTest_Click(object sender, EventArgs e)
    {
        int iTest = (int)cboInstructor.SelectedItem.GetValue("employee_id");
    }

At the line:

int iTest = (int)cboInstructor.SelectedItem.GetValue("employee_id");

cboInstructor.SelectedItem is null. Anyone have an idea why?

Answer 1

Anthony,

The SelectedItem is used to specify the item to select. Once an item is selected in the ASPxComboBox, you can use the Value or Text property to reference it.

http://documentation.devexpress.com/#AspNet/DevExpressWebASPxEditorsASPxComboBoxMembersTopicAll

This thread may also help you: http://community.devexpress.com/forums/t/61424.aspx

Thanks.