Page 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 CPL page reports, 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. | Copy Code |
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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.Extensibility; 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:"; /// Obtains and returns the resource, or returns null if it is not found. 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; } /// Returns a stream containing the specified image from the My Pictures folder, or null if the picture is not found. /// The path parameter is the URI of the image located in My Pictures, e.g. MyImages:logo.gif 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. | Copy Code |
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Imports GrapeCity.ActiveReports.Extensibility Imports System.Globalization Imports System.IO Imports System.Runtime.InteropServices Public Class MyPicturesLocator Inherits ResourceLocator Const UriSchemeMyImages As String = "MyPictures:" ' Obtains and returns the resource, or null if it is not found. ' The resourceInfo parameter contains the information about the resource to obtain. 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
In the Samples folder installed with the product, there is a Custom Resource Locator sample in a path like:
C:\Users\MyUserName\Documents\ComponentOne Samples\ActiveReports Developer 7\Page Reports\CPL\API\C#\CustomResourceLocator
This sample 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.