Filereader.readasdataurl Result Returning Format Exception When Entered In Convert.frombase64string

I'm using the following to convert an image to a base64 encoded string. On the client website in javascript: var reader = new FileReader(); reader.onloadend = function () {

Solution 1:

Okay, I have worked around this by using reader.readAsBinaryString instead and then converting this using btoa.

This seems to be accepted fine in Convert.FromBase64String

Solution 2:

I experienced the same issue and founds out that my complete dataurl contained not only padding characters at the end, but also padding characters in the middle of the dataurl. I used the following code to fix the base64string (but it still has a bug):

privatestaticstringgetCleanedBase64String(string base64String)
    {
        string tempString = base64String.Replace("_", "/").Replace("-", "+").Replace("=", "");
        return tempString + newstring('=', (4 - tempString.Length % 4) % 4);
    }