The input is not a valid Base-64 string as it contains a non-base 64 character

Question

I have a REST service that reads a file and sends it to another console application after converting it to Byte array and then to Base64 string. This part works, but when the same stream is received at the application, it gets manipulated and is no longer a valid Base64 string. Some junk characters are getting introduced into the stream.

The exception received when converting the stream back to Byte is

The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or a non-white space character among the padding characters

At Service:

[WebGet(UriTemplate = "ReadFile/Convert", ResponseFormat = WebMessageFormat.Json)]  
public string ExportToExcel()
  {
      string filetoexport = "D:\\SomeFile.xls";
      byte[] data = File.ReadAllBytes(filetoexport);
      var s = Convert.ToBase64String(data);
      return s;
  }

At Application:

       var client = new RestClient("http://localhost:56877/User/");
       var request = new RestRequest("ReadFile/Convert", RestSharp.Method.GET);
       request.AddHeader("Accept", "application/Json");
       request.AddHeader("Content-Type", "application/Json");
       request.OnBeforeDeserialization = resp => {resp.ContentType =    "application/Json";};
       var result = client.Execute(request);
       byte[] d = Convert.FromBase64String(result.Content);

The updated code is helpful. Now we need to see the string that you send (i.e. `s` on the service) and the content that's received (i.e. `result.content`. You don't need to post the entire string, just up to the first mangled character (or, if that's still too long, some substrings that show what was sent and what was received). — Jim Mischel, Feb 27 '13 at 14:21
@JimMischel yeah, i noticed that '/' is getting replaced with '\/' — Rohit Verma, Feb 27 '13 at 14:22
@RohitVerma For the slash getting replaced, is that in the raw HTML contents (Fiddler will tell you), or in `result.Content`? That will tell you if the problem is with the server or the client. — Joe Enos, Feb 27 '13 at 15:13
The error could also be related to a padding issue @see : https://stackoverflow.com/a/50525594/5102373 — Marc_Alx, Sep 27 '19 at 15:21

bendecko · Answer 1 · 2017-06-07T07:13:10.073

155

Check if your image data contains some header information at the beginning:

imageCode = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAMgAAABkC...

This will cause the above error.

Just remove everything in front of and including the first comma, and you good to go.

imageCode = "iVBORw0KGgoAAAANSUhEUgAAAMgAAABkC...

edited Jun 07 '17 at 07:13

answered May 29 '15 at 09:22

bendecko

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Had this exact issue somehow. Logic is to remove everything after `,` if `data:` is present. Bam. Working now. – Maxime Rouiller Jun 14 '16 at 13:14
var cleanerBase64 = imageCode.Substring(22); // remove data:image/png;base64 – mejiamanuel57 Nov 08 '18 at 21:22
4

Just a little bit of code to help...... if (this.imageCode.Contains(',')) this.imageCode = this.imageCode.Substring(this.imageCode.IndexOf(",") + 1, this.imageCode.Length - (this.imageCode.IndexOf(",") + 1)); – Toby Simmerling Jul 16 '19 at 09:15
3

I would use: .Split(',')[1] – Verthosa Jul 22 '19 at 11:35
5

`str.Substring(str.LastIndexOf(',') + 1)` should do it. – Alisson Reinaldo Silva Oct 29 '19 at 13:08
solved my problem. I was trying to save the base64 string to azure endpoint. After removed the header str, it worked. works like magic, thank you! – RainCast May 07 '20 at 07:42
this worked for me as well. I'm wondering if there's any reason why Convert.FromBase64String doesn't handle this scenario – kurdemol94 May 21 '21 at 10:27
I came here but had this message but with smtp issue on login. Turns out the office365 user email account was not licensed/mail setup with the right options. So there error for me was a red herring. – MTMDev Jun 15 '23 at 12:02

score 95 · Answer 2 · answered Feb 27 '13 at 14:09

95

Very possibly it's getting converted to a modified Base64, where the + and / characters are changed to - and _. See http://en.wikipedia.org/wiki/Base64#Implementations_and_history

If that's the case, you need to change it back:

string converted = base64String.Replace('-', '+');
converted = converted.Replace('_', '/');

answered Feb 27 '13 at 14:09

Jim Mischel

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I got this done ....Thanks to you!! Replacing the characters with the appropriate ones. But is this a concrete solution ? i mean how can i guarantee that for all the files this will be the character to be replaced ? – Rohit Verma Feb 27 '13 at 14:52
2

@RohitVerma: I don't know. You need to find out where those characters are getting changed, and determine if it's likely to change any other characters. I'm not familiar with RestSharp, so I can't offer any advice there. If my response answered your question, it's customary to mark it as the accepted answer. (Click the checkmark next to the answer on the left.) – Jim Mischel Feb 27 '13 at 15:14
OMG Thank you! This and adding the necessary padding "=" characters solved my problem. The decrypt function in Azure's Key Vault REST API needs this process and doesn't document it. – Brian Jul 08 '19 at 23:42

score 42 · Answer 3 · answered Mar 29 '16 at 09:40

42

We can remove unnecessary string input in front of the value.

string convert = hdnImage.Replace("data:image/png;base64,", String.Empty);

byte[] image64 = Convert.FromBase64String(convert);

answered Mar 29 '16 at 09:40

Hasan Tuna Oruç

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This solution worked for me. But this is specifically for png images. Is there any generalized syntax which replaces all kinds of image extensions? – Karan Desai Sep 01 '16 at 07:25
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i read your comment now. i dont try this but you can use this: hdnImage.Replace("data:image/png;base64,", String.Empty).Replace("data:image/jpg;base64,", String.Empty).Replace("data:image/bmp;base64,", String.Empty); again, i dont try this. please try and write for me. i will change. – Hasan Tuna Oruç Sep 05 '16 at 11:32

Amro Mustafa · Answer 4 · 2020-10-05T20:16:47.207

15

Remove the unnecessary string through Regex

Regex regex=new Regex(@"^[\w/\:.-]+;base64,");
base64File=regex.Replace(base64File,string.Empty);

edited Oct 05 '20 at 20:16

answered Oct 04 '20 at 18:07

Amro Mustafa

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Most efficient way of removing unnecessary string, Thanks – gm arif Dec 01 '22 at 12:11

score 7 · Answer 5 · answered Feb 27 '13 at 14:42

7

Since you're returning a string as JSON, that string will include the opening and closing quotes in the raw response. So your response should probably look like:

"abc123XYZ=="

or whatever...You can try confirming this with Fiddler.

My guess is that the result.Content is the raw string, including the quotes. If that's the case, then result.Content will need to be deserialized before you can use it.

answered Feb 27 '13 at 14:42

Joe Enos

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you are correct, this includes " " but the point here is that apart from the addition of these quotation marks other characters are also getting replaced. – Rohit Verma Feb 27 '13 at 14:57
Deserializing that string using a JSON serializer will take care of both the quotes and the escaped slash. Escaping your forward slashes with a backslash is something that some JSON serializers do - using a deserializer will turn \/ back into just plain / so that you'll get valid base-64. Since you're receiving JSON, it's always a good idea to parse that JSON properly, even if it is just a simple string. – Joe Enos Feb 27 '13 at 16:32

score 6 · Answer 6 · answered Aug 23 '17 at 13:37

6

Just in case you don't know the type of uploaded image, and you just you need to remove its base64 header:

 var imageParts = model.ImageAsString.Split(',').ToList<string>();
 //Exclude the header from base64 by taking second element in List.
 byte[] Image = Convert.FromBase64String(imageParts[1]);

answered Aug 23 '17 at 13:37

Mahdi Alkhatib

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split and To List ? use rather IndexOf and substring – Emmanuel Gleizer Jan 18 '18 at 09:03
see http://demeranville.com/battle-of-the-tokenizers-delimited-text-parser-performance/ and the question is also posted here: https://stackoverflow.com/questions/35388181/split-method-vs-substring-and-indexof – Emmanuel Gleizer Jan 25 '18 at 07:51

DevLoverUmar · Answer 7 · 2020-09-25T11:02:31.597

Probably the string would be like this data:image/jpeg;base64,/9j/4QN8RXh... First split for / and get the second token.

var StrAfterSlash = Face.Split('/')[1];

Then Split for ; and get the first token which will be the format. In my case it's jpeg.

var ImageFormat =StrAfterSlash.Split(';')[0];

Then remove the line data:image/jpeg;base64, for the collected format

CleanFaceData=Face.Replace($"data:image/{ImageFormat };base64,",string.Empty);

Alex Filipovici · Answer 8 · 2013-02-27T16:01:54.930

I arranged a similar context as you described and I faced the same error. I managed to get it working by removing the " from the beginning and the end of the content and by replacing \/ with /.

Here is the code snippet:

var result = client.Execute(request);
var response = result.Content
    .Substring(1, result.Content.Length - 2)
    .Replace(@"\/","/");
byte[] d = Convert.FromBase64String(response);

As an alternative, you might consider using XML for the response format:

[WebGet(UriTemplate = "ReadFile/Convert", ResponseFormat = WebMessageFormat.Xml)]  
public string ExportToExcel() { //... }

On the client side:

request.AddHeader("Accept", "application/xml");
request.AddHeader("Content-Type", "application/xml");
request.OnBeforeDeserialization = resp => { resp.ContentType = "application/xml"; };

var result = client.Execute(request);
var doc = new System.Xml.XmlDocument();
doc.LoadXml(result.Content);
var xml = doc.InnerText;
byte[] d = Convert.FromBase64String(xml);

score 3 · Answer 9 · answered Apr 06 '20 at 08:05

3

var spl = item.Split('/')[1];
var format =spl.Split(';')[0];           
stringconvert=item.Replace($"data:image/{format};base64,",String.Empty);

answered Apr 06 '20 at 08:05

mostafa kazemi

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Although this code might solve the problem, a good answer should also explain **what** the code does and **how** it helps. – BDL Apr 06 '20 at 09:25

score 3 · Answer 10 · answered Feb 01 '22 at 20:16

3

please check if there is no == as a postfix, just add == chars at last of string

// "........V/XeAeH/wALVWKtD8lz/AAAAABJRU5ErkJggg"
"........V/XeAeH/wALVWKtD8lz/AAAAABJRU5ErkJggg=="    /* yes */

answered Feb 01 '22 at 20:16

Mucahid Uslu

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score 2 · Answer 11 · answered Aug 03 '18 at 08:16

2

As Alex Filipovici mentioned the issue was a wrong encoding. The file I read in was UTF-8-BOM and threw the above error on Convert.FromBase64String(). Changing to UTF-8 did work without problems.

answered Aug 03 '18 at 08:16

testing

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score 1 · Answer 12 · answered Feb 03 '19 at 10:56

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And some times it started with double quotes, most of the times when you call API from dotNetCore 2 for getting file

string string64 = string64.Replace(@"""", string.Empty);
byte[] bytes = Convert.ToBase64String(string64);

answered Feb 03 '19 at 10:56

user193679

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Cannot convert from string to byte[] – Urasquirrel Feb 06 '19 at 19:11

score 0 · Answer 13 · answered Dec 28 '20 at 13:28

0

I get this error because a field was varbinary in sqlserver table instead of varchar.

answered Dec 28 '20 at 13:28

M Komaei

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The input is not a valid Base-64 string as it contains a non-base 64 character

13 Answers13

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