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.
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.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;
}
}
}
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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 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
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In the Samples folder installed with the product, there is a Custom Resource Locator sample in a path like:
C:\Users\MyUserName\Documents\GrapeCity Samples\ActiveReports 12\Page Reports\RDL\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.