How to: Manage Dashboard Parameters in Code

• Jun 13, 2018
• 3 minutes to read

The following example shows how to override an initial or user-defined dashboard parameter value by changing it in the CustomParameters event handler.

The effective parameter value is hidden from the end-user, and if you set the DashboardParameter.Visible property to false, the parameter itself will also be hidden.

A parameter named parameterState is added to the dashboard in code. It has a default value and a list of values to show in a look-up editor. A Dashboard Parameters dialog displays the values and allows the end-user to select a parameter value in the list. However, by handling the CustomParameters event, we can validate the parameter value and ignore the value provided by the end-user. To accomplish this, source data is filtered using a parameterState parameter.The value of this parameter is changed at runtime by handling the CustomParameters event which is raised before the dashboard sends a query to a database. Thus, only the value passed in the CustomParameters event is in effect.

Note

The complete sample project WinForms Dashboard - How to Manage Dashboard Parameters in Code is available in the DevExpress Examples repository.

C#

using DevExpress.XtraEditors;
using System.Linq;
using System.Collections.Generic;
using DevExpress.DashboardCommon;

namespace CustomParametersExample
{
    public partial class ViewerForm1 : XtraForm
    {
        public ViewerForm1()
        {
            InitializeComponent();
            dashboardViewer.CustomParameters += DashboardViewer_CustomParameters;
            dashboardViewer.DashboardSource = typeof(SampleDashboard);

            AddParameter(dashboardViewer.Dashboard);
            dashboardViewer.Dashboard.DataSources[0].Filter = "[State] In (?parameterState)";
            dashboardViewer.ReloadData();
        }

        private void AddParameter(Dashboard dBoard)
        {
            DashboardParameter myDashboardParameter = new DashboardParameter();
            StaticListLookUpSettings staticListLookUpSettings1 = new StaticListLookUpSettings();
            myDashboardParameter.AllowMultiselect = true;
            // Parameter values displayed in the look-up editor.
            staticListLookUpSettings1.Values = new string[] {"Alabama", "Ohio", "Utah"};
            myDashboardParameter.LookUpSettings = staticListLookUpSettings1;
            myDashboardParameter.Name = "parameterState";
            myDashboardParameter.Type = typeof(string);
            // Default parameter value.
            myDashboardParameter.Value = new List<string> { "Ohio", "Utah" };
            dBoard.Parameters.Add(myDashboardParameter);
        }

        private void DashboardViewer_CustomParameters(object sender, CustomParametersEventArgs e)
        {
            var customParameter = e.Parameters.FirstOrDefault(p => p.Name == "parameterState");
            if (customParameter != null)
            {
                // Actual value used when retrieving data from the data source.
                customParameter.Value = "Nevada";
            }
        }
    }
}

VB.NET

Imports DevExpress.XtraEditors
Imports System.Linq
Imports System.Collections.Generic
Imports DevExpress.DashboardCommon

Namespace CustomParametersExample
    Partial Public Class ViewerForm1
        Inherits XtraForm

        Public Sub New()
            InitializeComponent()
            AddHandler dashboardViewer.CustomParameters, AddressOf DashboardViewer_CustomParameters
            dashboardViewer.DashboardSource = GetType(SampleDashboard)

            AddParameter(dashboardViewer.Dashboard)
            dashboardViewer.Dashboard.DataSources(0).Filter = "[State] In (?parameterState)"
            dashboardViewer.ReloadData()
        End Sub

        Private Sub AddParameter(ByVal dBoard As Dashboard)
            Dim myDashboardParameter As New DashboardParameter()
            Dim staticListLookUpSettings1 As New StaticListLookUpSettings()
            myDashboardParameter.AllowMultiselect = True
            ' Parameter values displayed in the look-up editor.
            staticListLookUpSettings1.Values = New String() {"Alabama", "Ohio", "Utah"}
            myDashboardParameter.LookUpSettings = staticListLookUpSettings1
            myDashboardParameter.Name = "parameterState"
            myDashboardParameter.Type = GetType(String)
            ' Default parameter value.
            myDashboardParameter.Value = New List(Of String) From {"Ohio", "Utah"}
            dBoard.Parameters.Add(myDashboardParameter)
        End Sub

        Private Sub DashboardViewer_CustomParameters(ByVal sender As Object, ByVal e As CustomParametersEventArgs)
            Dim customParameter = e.Parameters.FirstOrDefault(Function(p) p.Name = "parameterState")
            If customParameter IsNot Nothing Then
                ' Actual value used when retrieving data from the data source.
                customParameter.Value = "Nevada"
            End If
        End Sub
    End Class
End Namespace