ActiveReports 13
Custom Resource Locator
ActiveReports 13 > ActiveReports User Guide > Concepts > Page Report/RDL Report Concepts > Custom Resource Locator

Page reports and RDL reports can resolve resources from your file system using file paths, but sometimes resources are preserved in very specific sources, such as a database. With RDL report, you can create a custom resource locator to read any resources that might be required by your reports from any type of location. You can use it for resources such as images and theme files, or for reports to use in drillthrough links, subreports, or master reports.

API

You can implement a custom resource locator by deriving from the ResourceLocator Class and overriding the GetResource method.

The GetResource method returns ParentUri and Value properties. The Value property contains the located resource as a memory stream. The ParentUri property contains the string URI of the parent of the resource within the resource hierarchy.

Here is the GetResource method used in the sample.

C# MyPicturesLocator.cs code showing usage of the GetResource Method from the Sample

C# code. Paste inside a class.
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using System;
using System.Collections.Generic;
using System.Drawing;
using System.Globalization;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using GrapeCity.ActiveReports.Samples.CustomResourceLocator.Properties;
namespace GrapeCity.ActiveReports.Samples.CustomResourceLocator
{
    /// Implementation of ResourceLocator which looks for resources in the My Pictures folder.
    internal sealed class MyPicturesLocator : ResourceLocator
    {
        private const string UriSchemeMyImages = "MyPictures:";
    '<summary>
'Look for the resources in My Pictures folder.
'</summary>
'<param name="resourceInfo">The information about the resource to be obtained. </param>
'<returns>The resource, null if it was not found. </returns> public override Resource GetResource(ResourceInfo resourceInfo) { Resource resource; string name = resourceInfo.Name; if (name == null || name.Length == 0) { throw new ArgumentException(Resources.ResourceNameIsNull, "name"); } Uri uri = new Uri(name); if (uri.GetLeftPart(UriPartial.Scheme).StartsWith(UriSchemeMyImages, true, CultureInfo.InvariantCulture)) { Stream stream = GetPictureFromSpecialFolder(uri); if (stream == null) { stream = new MemoryStream(); Resources.NoImage.Save(stream, Resources.NoImage.RawFormat); } resource = new Resource(stream, uri); } else { throw new InvalidOperationException(Resources.ResourceSchemeIsNotSupported); } return resource; } /// <summary>
/// Returns the specified image from My Pictures folder.
/// </summary>
/// <param name="path">The uri of the image located in My Pictures code, i.e. MyImages:logo.gif.</param>
/// <returns>The stream contains the image data or null if the picture can't be found or handled.</returns> private static Stream GetPictureFromSpecialFolder(Uri path) { int startPathPos = UriSchemeMyImages.Length; if (startPathPos >= path.ToString().Length) { return null; } string pictureName = path.ToString().Substring(startPathPos); string myPicturesPath = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures); if (!myPicturesPath.EndsWith("\\")) myPicturesPath += "\\"; string picturePath = Path.Combine(myPicturesPath, pictureName); if (!File.Exists(picturePath)) return null; MemoryStream stream = new MemoryStream(); try { Image picture = Image.FromFile(picturePath); picture.Save(stream, picture.RawFormat); stream.Position = 0; } catch(OutOfMemoryException) /// The file is not a valid image, or GDI+ doesn't support the image type. { return null; } catch(ExternalException) /// The image can't be saved. { return null; } return stream; } } }

Visual Basic MyPicturesLocator.vb code showing usage of the GetResource Method from the Sample

Visual Basic code. Paste inside a class.
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Imports System.Globalization
Imports System.IO
Imports System.Runtime.InteropServices

Public Class MyPicturesLocator
    Inherits ResourceLocator

    Const UriSchemeMyImages As String = "MyPictures:"

    '<summary>
'Look for the resources in My Pictures folder.
'</summary>
'<param name="resourceInfo">The information about the resource to be obtained. </param>
'<returns>The resource, null if it was not found. </returns> Public Overrides Function GetResource(ByVal resourceInfo As ResourceInfo) As Resource Dim resource As Resource Dim name As String = resourceInfo.Name If (String.IsNullOrEmpty(name)) Then Throw New ArgumentException(My.Resources.ResourceNameIsNull, "name") End If Dim uri As New Uri(name) If (Uri.GetLeftPart(UriPartial.Scheme).StartsWith(UriSchemeMyImages, True, CultureInfo.InvariantCulture)) Then Dim stream As Stream = GetPictureFromSpecialFolder(uri) If (stream Is Nothing) Then stream = New MemoryStream() My.Resources.NoImage.Save(stream, My.Resources.NoImage.RawFormat) End If resource = New Resource(stream, uri) Else Throw New InvalidOperationException(My.Resources.ResourceSchemeIsNotSupported) End If Return resource End Function Function GetPictureFromSpecialFolder(ByVal path As Uri) As Stream Dim startPathPos As Integer = UriSchemeMyImages.Length If (startPathPos >= path.ToString().Length) Then Return Nothing End If Dim pictureName As String = path.ToString().Substring(startPathPos) Dim myPicturesPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures) If (Not myPicturesPath.EndsWith("\\")) Then myPicturesPath += "\\" End If Dim picturePath As String = System.IO.Path.Combine(myPicturesPath, pictureName) If (Not File.Exists(picturePath)) Then Return Nothing End If Dim stream As New MemoryStream() Try Dim picture As Image = Image.FromFile(picturePath) picture.Save(stream, picture.RawFormat) stream.Position = 0 Catch ex As OutOfMemoryException ' The file is not a valid image, or GDI+ doesn't support the image type. Return Nothing Catch ex As ExternalException ' The image can't be saved. Return Nothing End Try Return stream End Function End Class

Sample

The product sample is located here:

<User Folder>\Documents\GrapeCity Samples\ActiveReports 13\Advanced\PageAndRDL\CustomResourceLocator\C# or VB.NET

contains a custom resource locator that looks for files in the current user’s My Pictures folder. It does this by looking for special MyPictures protocol.

See Also

Walkthroughs