Lesson 5 - Pass Multi-Value Parameters to Reports

• Jun 25, 2020
• 5 minutes to read

This example illustrates the process of creating a reporting application where an end-user can provide multiple values for an individual report parameter.

To learn how to allow the passing of multi-value parameters to your LightSwitch reports, do the following.

1. Create a LightSwitch project with the XtraReports extension enabled and add a WCF RIA service to the application (for more details, see Lesson 1 - Create a Data-Aware Report).
2. Add a data source. In this example, we will create a LightSwitch data source (named NorthWindData) based on theProducts and Categories tables of the sample Northwind database.

3. Add a query (named ProductsByCategories) to the Products table. In the created query, create a String parameter (named categories).

   

4. In the same window, expand the Write Code drop-down list and click the ProductsByCategories_PreprocessQuery method link to add the following code.

   C#

   using System;
   using System.Linq;
   // ... 
   
   namespace LightSwitchApplication {
       public partial class NorthWindDataService {
           partial void ProductsByCategories_PreprocessQuery(string categories, ref IQueryable<Product> query) {
               if (!String.IsNullOrEmpty(categories)) {
                   var ids = Array.ConvertAll(categories.Split(';'), x => int.Parse(x));
                   query = query.Where(x => ids.Contains(x.Category.CategoryID));
               }
           }
       }
   }
   

   VB.NET

   Imports System
   Imports System.Linq
   ' ... 
   
   Namespace LightSwitchApplication
       Public Partial Class NorthWindDataService
           Private Partial Sub ProductsByCategories_PreprocessQuery(categories As String, _ 
           ByRef query As IQueryable(Of LightSwitchApplication.Product))
               If Not String.IsNullOrEmpty(categories) Then 
                   Dim ids = Array.ConvertAll(categories.Split(";"), _ 
                       Function(x)
                           Return Integer.Parse(x)
                       End Function)
                   query = query.Where(Function(x) ids.Contains(x.Category.CategoryID)) 
               End If 
           End Sub 
       End Class 
   End Namespace
   

5. Add a new XtraReport to the Server part of the application, bind the report to the created query and adjust the report’s layout.

   

6. Add a Report Preview screen, switch to its code and write the following logic in it.

   C#

   using System;
   using System.Collections.Generic;
   using System.Globalization;
   using System.Windows.Data;
   using DevExpress.Utils;
   using DevExpress.Xpf.Editors;
   using DevExpress.Xpf.Printing;
   // ... 
   
   namespace LightSwitchApplication {
       public partial class ReportPreviewScreen {
           class CategoryInfo {
               public int ID { get; set; }
               public string Name { get; set; }
               public override bool Equals(object obj) {
                   CategoryInfo other = obj as CategoryInfo;
                   return other != null && other.Name == Name && other.ID == ID;
               }
               public override int GetHashCode() {
                   return HashCodeHelper.CalcHashCode(Name, ID);
               }
           }
   
           class CategoryIDsToStringConverter : IValueConverter {
               public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
                   string categories = value as string;
                   if (string.IsNullOrEmpty(categories)) {
                       return null;
                   }
                   return ArrayHelper.ConvertAll(categories.Split(';'), x => int.Parse(x));
               }
   
               public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
                   IEnumerable<object> ids = value as IEnumerable<object>;
                   if (ids == null) {
                       return null;
                   }
                   return String.Join(";", ids);
               }
           }
   
           // Do not rename the CustomizeReportPreviewModel method  
           // because it is used to access the ReportPreviewModel that is associated with this Report Preview Screen. 
           // You can remove this method if you do not need to access the ReportPreviewModel. 
           public void CustomizeReportPreviewModel(DevExpress.Xpf.Printing.ReportPreviewModel model) {
               model.CustomizeParameterEditors += model_CustomizeParameterEditors;
           }
   
           List<CategoryInfo> categories;
   
           void model_CustomizeParameterEditors(object sender, CustomizeParameterEditorsEventArgs e) {
               if (e.Parameter.Name == "categories") {
                   ComboBoxEdit comboBox = new ComboBoxEdit();
                   comboBox.StyleSettings = new CheckedComboBoxStyleSettings();
                   comboBox.DisplayMember = "Name";
                   comboBox.ValueMember = "ID";
                   comboBox.ItemsSource = categories;
                   e.Editor = comboBox;
                   e.BoundDataMember = "EditValue";
                   e.BoundDataConverter = new CategoryIDsToStringConverter();
               }
           }
   
           partial void ReportPreviewScreen_Activated() {
               // Assign the name of the report that you want to preview in this screen. 
               this.ReportTypeName = "LightSwitchApplication.XtraReport1";
               categories = new List<CategoryInfo>();
               foreach (Category category in new DataWorkspace().NorthWindData.Categories) {
                   categories.Add(new CategoryInfo() { Name = category.CategoryName, ID = category.CategoryID });
               }
           }
       }
   }
   

   VB.NET

   Imports DevExpress.Utils
   Imports System.Windows.Data
   Imports DevExpress.Xpf.Editors
   ' ... 
   
   Namespace LightSwitchApplication
   
     Public Class ReportPreviewScreen
   
       Dim categories As List(Of CategoryInfo)
       Class CategoryInfo
         Private _iD As Integer 
         Private _name As String 
         Public Property ID As Integer 
           Get 
             Return _iD
           End Get 
           Set(ByVal Value As Integer)
             _iD = Value
           End Set 
         End Property 
   
         Public Property Name As String 
           Get 
             Return _name
           End Get 
           Set(ByVal Value As String)
             _name = Value
           End Set 
         End Property 
   
         Public Overrides Function Equals(obj As Object) As Boolean 
           Dim other As CategoryInfo
           other = CType(obj, CategoryInfo)
           If other Is Nothing Then 
             Return False 
           End If 
           Return other.Name = Name And other.ID = ID
         End Function 
   
         Public Overrides Function GetHashCode() As Integer 
           Return HashCodeHelper.CalcHashCode(Name, ID)
         End Function 
       End Class 
   
       Class CategoryIDsToStringConverter
         Implements IValueConverter
   
         Public Function Convert(value As Object, targetType As Type, parameter As Object, _ 
         culture As Globalization.CultureInfo) As Object Implements IValueConverter.Convert
           Dim categories As String 
           categories = CType(value, String)
           If String.IsNullOrEmpty(categories) Then 
             Return Nothing 
           End If 
           Return ArrayHelper.ConvertAll(categories.Split(","), _ 
               Function(x)
                   Return Integer.Parse(x)
               End Function)
         End Function 
   
         Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, _ 
         culture As Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack
           Dim ids As IEnumerable(Of Object)
           ids = CType(value, IEnumerable(Of Object))
           If ids Is Nothing Then 
             Return Nothing 
           End If 
           Return String.Join(",", ids)
         End Function 
       End Class 
   
       ' Do not rename the CustomizeReportPreviewModel method  
       ' because it is used to access the ReportPreviewModel that is associated with this Report Preview Screen. 
       ' You can remove this method if you do not need to access the ReportPreviewModel. 
       Public Sub CustomizeReportPreviewModel(model As DevExpress.Xpf.Printing.ReportPreviewModel)
         AddHandler model.CustomizeParameterEditors, AddressOf Me.model_CustomizeParameterEditors
       End Sub 
   
       Private Sub model_CustomizeParameterEditors(sender As Object, _ 
       e As DevExpress.Xpf.Printing.CustomizeParameterEditorsEventArgs)
         If e.Parameter.Name = "categories" Then 
           Dim comboBox As New ComboBoxEdit()
           comboBox.StyleSettings = New CheckedComboBoxStyleSettings()
           comboBox.DisplayMember = "Name" 
           comboBox.ValueMember = "ID" 
           comboBox.ItemsSource = categories
           e.Editor = comboBox
           e.BoundDataMember = "EditValue" 
           e.BoundDataConverter = New CategoryIDsToStringConverter()
         End If 
       End Sub 
   
       Private Sub ReportPreviewScreen_Activated()
         ' Assign the name of the report that you want to preview in this screen. 
         Me.ReportTypeName = "XtraReport1" 
         categories = New List(Of CategoryInfo)()
         For Each category As Category In New DataWorkspace().NorthWind_XtraReportsData.Categories
           Dim info As New CategoryInfo
           info.Name = category.CategoryName
           info.ID = category.CategoryID
           categories.Add(info)
         Next category
       End Sub 
     End Class 
   End Namespace
   

Run the application and view the result.