Update SSRS report parameters using custom ASP.NET controls - asp.net

Question

I have a ASP.NET web app, which uses SSRS 2008 R2 on another machine in Native mode. The app has a page for generation reports created in SSRS.
I use my own custom controls for report parameters. After all the parameters are set, the page generates the report using a hidden ReportViewer control.
Here is the page layout:
<asp:Repeater ID="rptParameters" runat="server">
<ItemTemplate>
<tr>
<td class="label">
<asp:Literal ID="label" runat="server"/>:
</td>
<td class="control">
<asp:TextBox ID="tbx" runat="server" Visible="false"/>
<my:tsJCalendar ID="calendar" runat="server" GeneratePostback="false" HasValidation="true" ErrorDisplay="None" CompareMessage="Date must be in valid 'mm/dd/yyyy' format!" Visible="false"/>
<asp:RadioButtonList ID="radioList" runat="server" Visible="false"
RepeatDirection="Horizontal" RepeatLayout="Flow">
<asp:ListItem Text="True" Value="1"></asp:ListItem>
<asp:ListItem Text="False" Value="0"></asp:ListItem>
</asp:RadioButtonList>
<asp:DropDownList ID="ddl" runat="server" Visible="false"></asp:DropDownList>
<asp:HiddenField ID="hdnForDdl" runat="server"/>
</td>
<td width="22px"></td>
</ItemTemplate>
<AlternatingItemTemplate>
<td class="label">
<asp:Literal ID="label" runat="server"/>:
</td>
<td class="control">
<asp:TextBox ID="tbx" runat="server" Visible="false"/>
<my:tsJCalendar ID="calendar" runat="server" GeneratePostback="false" HasValidation="True" ErrorDisplay="None" CompareMessage="Date must be in valid 'mm/dd/yyyy' format!" Visible="false"/>
<asp:RadioButtonList ID="radioList" runat="server" Visible="false">
<asp:ListItem Text="True" Value="1"></asp:ListItem>
<asp:ListItem Text="False" Value="0"></asp:ListItem>
</asp:RadioButtonList>
<asp:DropDownList ID="ddl" runat="server" Visible="false"></asp:DropDownList>
<asp:HiddenField ID="hdnForDdl" runat="server"/>
</td>
</tr>
</AlternatingItemTemplate>
</asp:Repeater>
<rsweb:ReportViewer ID="rvReports" runat="server" Width="100%"
ShowReportBody="False" ShowPromptAreaButton="false" ShowWaitControlCancelLink="false"
AsyncRendering="false" Visible="false">
</rsweb:ReportViewer>
<hr />
<asp:Button ID="btnRun" runat="server" Text="Run Report" />
To generate custom parameter controls I use the repeater and show an appropriate control according by the report parameter type.
I am working with SSRS using its ReportingService2005 webservice. E.g. on the first page loading, I am getting report parameters using this code:
Private Function GetParameterReports(values As ParameterValue()) As ReportParameter()
Dim rs As New ReportingService2005()
rs.Credentials = New MyReportCredentials().NetworkCredentials
Dim forRendering As Boolean = True
Dim historyID As String = Nothing
Dim credentials As DataSourceCredentials() = Nothing
Dim paramInfos As ReportParameter() = rs.GetReportParameters(ReportPath, historyID, forRendering, values, credentials)
Return paramInfos
End Function
The 'values' parameter is Nothing for the first time. However, if a parameter depends on other parameters, I do a postback, and pass report values to the report to get updated parameters, using the same GetParameterReports() method.
All the reports have a special field, 'user_id', which is the identifier of the logged in user. I must set this parameter manually in the code, and I am trying to do this by using 2 ways:
Dim Values As New List(Of ParameterValue)()
Dim singleUserParameter As New ParameterValue()
With singleUserParameter
.Name = "user_id"
.Value = Security.CurrentUserPeopleID
End With
Values.Add(singleUserParameter)
paramInfos = GetParameterReports(Values.ToArray)
and
Dim userIdParameter As New ReportParameter()
userIdParameter.DefaultValues = New String() {Security.CurrentUserPeopleID.ToString()}
userIdParameter.PromptUser = False
Dim rs As New ReportingService2005()
rs.Credentials = New MyReportCredentials().NetworkCredentials
rs.SetReportParameters(ReportPath, paramInfos)
paramInfos = GetParameterReports(Nothing)
Some of the report parameters depend on the 'user_id', but, unfortunately, after calling ReportingService2005.GetReportParameters() with the passed 'user_id' value, dependent parameters still don't have DefaultValues.
Could you help to understand whether I am doing something wrong while setting the report parameters values, or the reason is in how the SSRS report was created?