SnapControl.BeforeLoadCustomAssembly Event

Occurs when the control loads a report template (.snx file) containing the Entity Framework data source originated from a compiled assembly.

Namespace: DevExpress.Snap

Assembly: DevExpress.Snap.v18.2.dll

Declaration

C#

public event BeforeLoadCustomAssemblyEventHandler BeforeLoadCustomAssembly

VB.NET

Public Event BeforeLoadCustomAssembly As BeforeLoadCustomAssemblyEventHandler

Event Data

The BeforeLoadCustomAssembly event's data class is BeforeLoadCustomAssemblyEventArgs. The following properties provide information specific to this event:

Property	Description
AllowLoading	Specifies whether loading a custom assembly is allowed.
AssemblyPath	Specifies the path to a requested assembly.
ContextName	Specifies the type to load from a custom assembly.

Remarks

When a report template is loading, the SnapControl creates a data source from the string serilalized in the .snx file. The EFDataSource.BeforeLoadCustomAssemblyGlobal event allows you to specify whether to load custom data assemblies in the application. If the loading is allowed, an attempt to load the Entity Framework data model as the Snap data source fires the BeforeLoadCustomAssembly event. If the BeforeLoadCustomAssemblyEventArgs.AllowLoading is set to true, the assembly is loaded.

Example

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-prevent-loading-untrusted-custom-assembly-in-ef-data-model-t408545

Form1.cs

using System;
using System.Windows.Forms;

namespace EFDataTest {
    public partial class Form1 : DevExpress.XtraBars.Ribbon.RibbonForm {
        public Form1() {
            InitializeComponent();
            // Handle this event to decide whether this application allows loading a custom data assembly.
            DevExpress.DataAccess.EntityFramework.EFDataSource.BeforeLoadCustomAssemblyGlobal += EFDataSource_BeforeLoadCustomAssemblyGlobal;
            // Handle this event to allow loading a custom data assembly when the SnapControl queries the data source.
            this.snapControl1.BeforeLoadCustomAssembly += SnapControl1_BeforeLoadCustomAssembly;
    }

        private void EFDataSource_BeforeLoadCustomAssemblyGlobal(object sender, DevExpress.DataAccess.EntityFramework.BeforeLoadCustomAssemblyEventArgs args) {
            args.AllowLoading = true;
        }

        private void SnapControl1_BeforeLoadCustomAssembly(object sender, DevExpress.DataAccess.EntityFramework.BeforeLoadCustomAssemblyEventArgs args) {
            // Decide whether to load a custom assembly.
            args.AllowLoading = MessageBox.Show(String.Format("Do you want to load data from {0}?", args.AssemblyPath),
                    "Snap Security Warning", MessageBoxButtons.YesNo) == DialogResult.Yes;
        }

        private void Form1_Load(object sender, EventArgs e) {
            // Create test.snx template and save it.
            MyHelper.CreateAndSaveReportTemplate(this.snapControl1);
            this.snapControl1.CreateNewDocument();
            this.snapControl1.BeforeLoadCustomAssembly += SnapControl1_BeforeLoadCustomAssembly;
        }

        private void btnLoadTemplateWithData_ItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e) {
            // Load template with data.
            if (System.IO.File.Exists("test.snx")) {
                this.snapControl1.LoadDocument("test.snx");
                this.snapControl1.Options.SnapMailMergeVisualOptions.DataSourceName = "Contacts";
            }
        }

        private void tglShowWizardBrowseButton_CheckedChanged(object sender, DevExpress.XtraBars.ItemClickEventArgs e) {
            // Show the button in the Data Source Wizard to launch the "Browse for assembly" dialog. 
            this.snapControl1.Options.DataSourceWizardOptions.EFWizardSettings.ShowBrowseButton = tglShowWizardBrowseButton.Checked;
        }
    }
}

Form1.vb

Imports System
Imports System.Windows.Forms

Namespace EFDataTest
    Partial Public Class Form1
        Inherits DevExpress.XtraBars.Ribbon.RibbonForm

        Public Sub New()
            InitializeComponent()
            ' Handle this event to decide whether this application allows loading a custom data assembly.
            AddHandler DevExpress.DataAccess.EntityFramework.EFDataSource.BeforeLoadCustomAssemblyGlobal, AddressOf EFDataSource_BeforeLoadCustomAssemblyGlobal
            ' Handle this event to allow loading a custom data assembly when the SnapControl queries the data source.
            AddHandler Me.snapControl1.BeforeLoadCustomAssembly, AddressOf SnapControl1_BeforeLoadCustomAssembly
        End Sub

        Private Sub EFDataSource_BeforeLoadCustomAssemblyGlobal(ByVal sender As Object, ByVal args As DevExpress.DataAccess.EntityFramework.BeforeLoadCustomAssemblyEventArgs)
            args.AllowLoading = True
        End Sub

        Private Sub SnapControl1_BeforeLoadCustomAssembly(ByVal sender As Object, ByVal args As DevExpress.DataAccess.EntityFramework.BeforeLoadCustomAssemblyEventArgs)
            ' Decide whether to load a custom assembly.
            args.AllowLoading = MessageBox.Show(String.Format("Do you want to load data from {0}?", args.AssemblyPath), "Snap Security Warning", MessageBoxButtons.YesNo) = DialogResult.Yes
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
            ' Create test.snx template and save it.
            MyHelper.CreateAndSaveReportTemplate(Me.snapControl1)
            Me.snapControl1.CreateNewDocument()
            AddHandler Me.snapControl1.BeforeLoadCustomAssembly, AddressOf SnapControl1_BeforeLoadCustomAssembly
        End Sub

        Private Sub btnLoadTemplateWithData_ItemClick(ByVal sender As Object, ByVal e As DevExpress.XtraBars.ItemClickEventArgs) Handles btnLoadTemplateData.ItemClick
            ' Load template with data.
            If System.IO.File.Exists("test.snx") Then
                Me.snapControl1.LoadDocument("test.snx")
                Me.snapControl1.Options.SnapMailMergeVisualOptions.DataSourceName = "Contacts"
            End If
        End Sub

        Private Sub tglShowWizardBrowseButton_CheckedChanged(ByVal sender As Object, ByVal e As DevExpress.XtraBars.ItemClickEventArgs) Handles tglShowWizardBrowseButton.CheckedChanged
            ' Show the button in the Data Source Wizard to launch the "Browse for assembly" dialog. 
            Me.snapControl1.Options.DataSourceWizardOptions.EFWizardSettings.ShowBrowseButton = tglShowWizardBrowseButton.Checked
        End Sub
    End Class
End Namespace

Implements

BeforeLoadCustomAssembly