ReportViewer resets parameters after submit

Question

I'm showing a remote report in a ReportViewer control. The report loads with a few default parameters. So far everything is ok.

But when i change a few input values and hit View Report then the report simply shows the data with the default values. The parameters that i changed in the input fields are also reset.

All the code i have is this:

apsx

<rsweb:ReportViewer ID="ReportViewer1" runat="server" Font-Names="Verdana"
    Font-Size="8pt" Height="642px" ProcessingMode="Remote" Width="100%">
    <ServerReport ReportPath="http://server.com/Product/Dashboards/test.rdl" 
        ReportServerUrl="http://server.com/ReportServer" />
</rsweb:ReportViewer>

The CodeBehind is basically empty. All it has now is an empty Page_Load.

That is all my code.

But it feels like a ViewState issue? But I am not sure where to look.

Anyone any idea why the parameters are resrt when I press on the View Report button?

Answer 1

I solved this by setting the parameters myself in the Code Behind. So when the report is submitted, i then get all the entered data, put that in a ReportParameters collection.

But unfortunately this wasn't as easy and straight forward as one would think. At first you might think this is stored in: YourReport.ServerReport.GetParameters(). But that is not the case!

To get the submitted values from your report you can use the following code:

Get report submitted parameters

public ReportParameter[] GetCurrentParameters(Microsoft.Reporting.WebForms.ReportViewer viewer)
{
    Control params1Area = FindParametersArea(viewer);
    List<ReportParameter> params1 = new List<ReportParameter>();
    FindParameters(params1Area, params1);
    return params1.ToArray();
}

private Control FindParametersArea(Microsoft.Reporting.WebForms.ReportViewer viewer)
{
    foreach (Control child in viewer.Controls)
    {
        if (child.GetType().Name == "ParametersArea")
            return child;
    }


    return null;
}

private void FindParameters(Control parent, List<ReportParameter> params1)
{
    Type _ParameterControlType = System.Reflection.Assembly.GetAssembly(typeof(Microsoft.Reporting.WebForms.ReportViewer)).GetType("Microsoft.Reporting.WebForms.BaseParameterInputControl");

    ReportParameter param;
    Microsoft.Reporting.WebForms.ReportParameterInfo paramInfo;
    String[] paramValues;
    foreach (Control child in parent.Controls)
    {
        if (_ParameterControlType.IsAssignableFrom(child.GetType()))
        {
            paramInfo = (Microsoft.Reporting.WebForms.ReportParameterInfo)GetPropertyValue(child, "ReportParameter");
            if (paramInfo == null)
                continue;


            paramValues = (string[])GetPropertyValue(child, "CurrentValue");
            if (paramValues != null && paramValues.Length > 0)
            {
                param = new ReportParameter();
                param.Name = paramInfo.Name;
                param.Values.AddRange(paramValues);
                params1.Add(param);
            }
        }
        FindParameters(child, params1);
    }
}

public object GetPropertyValue(object target, string propertyName)
{
    return target.GetType().GetProperty(propertyName, System.Reflection.BindingFlags.IgnoreCase | System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Public).GetValue(target, null);
}

Source: http://forums.asp.net/t/1057747.aspx/1 (Also Visual Basic examples)

You invoke those methods by just using the following line of code. Preferably in a if(IsPostBack) scope within your Page_Load for example.

ReportParameter[] reportParameters = GetCurrentParameters(ReportViewer1);

It is then possible to overwrite the submitted values if you also have custom textfields. You can easily do that like so:

reportParameters[4] = new ReportParameter("year", "2013", true);

You obviously have to know what param is stored at index 4. But you could also make an easy lookup function that searches for the reportParameter with a specific name. So in my case year.

Simple parameter lookup

protected void ChangeParameterValue(String name, String newValue, ref ReportParameter[] parameters)
{
    foreach (ReportParameter param in parameters)
    {
        if (String.Equals(param.Name, name))
        {
            param.Values[0] = newValue;
            break;
        }
    }
}

You use that like so:

ChangeParameterValue("year", "2013", ref reportParameters);

This way you don't have to worry about at what index a certain parameter is placed.