How to: Manage Dashboard Parameters in Code

• Mar 19, 2019
• 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 WPF Dashboard - How to Manage Dashboard Parameters in Code is available in the DevExpress Examples repository.

C#

using System;
using DevExpress.Mvvm.DataAnnotations;
using DevExpress.Mvvm;
using DevExpress.Mvvm.POCO;
using System.Linq;
using DevExpress.DashboardCommon;
using System.Collections.Generic;

namespace WPF_Dashboard_CustomParameters.ViewModels
{
    [POCOViewModel]
    public class MyViewModel
    {
        protected MyViewModel() {
            //Dashboard = new SampleDashboard(); 
            Dashboard dashboard = new Dashboard();
            dashboard.LoadFromXml("Data\\SampleDashboard.xml");
            AddParameter(dashboard);
            ModifyFilter(dashboard);
            Dashboard = dashboard;
        }
        public virtual DevExpress.DashboardCommon.Dashboard Dashboard { get; set; }
        private void ModifyFilter(Dashboard dashboard)
        {
            dashboard.DataSources[0].Filter = "[State] In (?parameterState)";
        }
        private void AddParameter(Dashboard dashboard)
        {
            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" };
            dashboard.Parameters.Add(myDashboardParameter);
        }
        public void OnCustomParameters(DevExpress.DashboardCommon.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 System
Imports DevExpress.Mvvm.DataAnnotations
Imports DevExpress.Mvvm
Imports DevExpress.Mvvm.POCO
Imports System.Linq
Imports DevExpress.DashboardCommon
Imports System.Collections.Generic

Namespace WPF_Dashboard_CustomParameters.ViewModels
    <POCOViewModel> _
    Public Class MyViewModel
        Protected Sub New()
            'Dashboard = new SampleDashboard(); 

            Dim dashboard_Renamed As New Dashboard()
            dashboard_Renamed.LoadFromXml("Data\SampleDashboard.xml")
            AddParameter(dashboard_Renamed)
            ModifyFilter(dashboard_Renamed)
            Dashboard = dashboard_Renamed
        End Sub
        Public Overridable Property Dashboard() As DevExpress.DashboardCommon.Dashboard
        Private Sub ModifyFilter(ByVal dashboard As Dashboard)
            dashboard.DataSources(0).Filter = "[State] In (?parameterState)"
        End Sub
        Private Sub AddParameter(ByVal dashboard 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"}
            dashboard.Parameters.Add(myDashboardParameter)
        End Sub
        Public Sub OnCustomParameters(ByVal e As DevExpress.DashboardCommon.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