问题
I'm trying to display image(base64 string) using parameter(@CustomerSign) in RDLC report (I'm rendering PDF file from report and I'm seeing PDF file)
I've configured image property as below:
Select the image source : Database
Use this field :
=Convert.FromBase64String(Parameters!CustomerSign.Value)
Use this MIME type: image/png
And passing parameter:
ReportParameter CustomerSign = new ReportParameter("CustomerSign", obj.SignImage);
rptvw.LocalReport.SetParameters(CustomerSign);
But the image showing red Cross [X] instead of image, and doesn't gives an error!
What could be the issue?
I've also tried: How can I render a PNG image (as a memory stream) onto a .NET ReportViewer report surface
回答1:
Support for images is pretty limited, this MSDN article discusses what you can do.
Seems somewhat obvious from the question that embedding them in the report is not an option. But you can specify an external dbase as a source. Beware the EnableExternalImages property you have to set, as documented by the MSDN article. Seems the way to go, the question is not detailed enough, you might have to provide a suitable table with the desired image in your code.
回答2:
First, check the Visual Studio output window. Any RDLC errors that you get should appear there when debugging.
For example, I was getting an error saying that I was passing an invalid base64 string.
If you see:
Warning: The value of the ImageData property for the image ‘Image’ is “=Convert.From...”, which is not a valid ImageData. (rsInvalidDatabaseImageProperty)
this seems to mean that an exception was thrown and so the expression did not evaluate and was passed as raw text (and so this message says that the raw text is not valid image data). The previous line in the output window should contain the actual error that caused the problem.
In my case, following the pattern that you are using (thanks), my problem ended up being that my base64 in the database was prefixed with data:image/png;base64, since it was being pulled from and written to an html image element.
To remove that prefix turned my RDLC expression to:
=Convert.FromBase64String(CStr(Parameters!Base64.Value).Substring(22))
What I would suggest is pulling a base 64 string out of the database and confirm that it does actually work as an image. Try putting it into a base64 image viewer (for example: https://codebeautify.org/base64-to-image-converter). (Although in my case I guess that wouldn't have helped since that site still works even with that prefix.)
回答3:
=System.Convert.FromBase64String(Parameters!Logo.Value)
来源：https://stackoverflow.com/questions/42020490/base64-image-doesnt-display-on-render-pdf-from-rdlc-report