SSRS Show Base64 String or Byte Array From URL as Image

问题

I have a wevservice that returns an image as a Base64 string, or as a byte array, that I need to show as an image in SSRS. Not sure how to do that.

I tried using an expression in the image properties:

=System.Convert.FromBase64String("http://localhost:5460/api/Report/GetImage")

but that does not work. How do I get the string or array from the URL, then display it as an image?

I have also tried a Code block, but when I try

Dim hwr As System.Net.HttpWebRequest
hwr = System.Net.WebRequest.Create("http://localhost:5460/api/Report/GetImage")

I get the error:

Severity    Code    Description Project File    Line    Suppression State
Warning     [rsRuntimeErrorInExpression] The Value expression for the textrun 'Textbox2.Paragraphs[0].TextRuns[0]' contains an error: 
Insufficient permissions for setting the configuration property 'maximumErrorResponseLength'. (c:\program files (x86)\microsoft visual studio\2017\sql\common7\ide\commonextensions\microsoft\ssrs\PreviewProcessingService.exe.Config line 42)     C:\Users\Desktop\REP90011\REP90011.rdl  0   

This is on my local machine, not on the SSRS server or through IIS. Just through the preview pane in VS 2017.

回答1:

The problem was that I need to allow permissions in the file RSPreviewPolicy.config on my desktop to be 'FullTrust' instead of 'Nothing' in order to be able to use 'System.Net.WebRequest.Create'.

Edit: I have been asked to expand on how my process works, so here it is:

I have a webservice that fetches an image and returns it as a base64 string.

Put an image object on the report, set it to 'Database', 'image/bmp', and use this expression as the field:

=Convert.FromBase64String(Code.GetImageString("http://localhost:5460/api/Report/GetImage")

The URL being the webservice that returns the string.

The function GetImageString is in the Code section of report properties:

Public Function GetImageString(Url As String) As String
   'create web request
   Dim hwr As System.Net.HttpWebRequest
   'this line is what I needed to change the permissions for
   hwr = System.Net.WebRequest.Create(Url) 
   hwr .Credentials = System.Net.CredentialCache.DefaultCredentials
   'get response from request
   Dim wr As System.Net.WebResponse
   wr = hwr.GetResponse()
   'get stream from response
   Dim sr as System.IO.Stream
   sr = wr.GetResponseStream()
   'read response stream
   Dim read As IO.StreamReader
   read = new IO.StreamReader(sr, System.Text.Encoding.UTF8)
   'convert stream to string
   Dim result as string
   result = read.ReadToEnd
   return result.substring(1, result.length - 2) 'remove first and last characters, it's putting in quotes
 End Function

In VS 2017 this worked fine on my desktop. In VS 2019 it shows a red x on my desktop, but still works when deployed to the server.

来源：https://stackoverflow.com/questions/62093125/ssrs-show-base64-string-or-byte-array-from-url-as-image