CODEWITHSUNDEEP
c#checksum
New Developer
New Developer

Reputation: 3305

How to check transferred file is not changed

I have a web service and I am going to access the database over that web service. I am going to save a text file to my DB using web service.

Before saving file to the DB I want to make sure that that the file not changed.

I have no idea to how to do this. Can please anybody explain me how to do this. Specifying the steps would be enough.

EDIT

I am passing my text file to the web service as byte array. In other words I want to make sure all the bytes which I sent, has received to the web service as it is.(not corrupted nor loose of data). I have control over the web service as well.

Upvotes: 1

Views: 644

Answers (2)

Ron.B.I
Ron.B.I

Reputation: 2766

You generally don't need to check that, you have different communication layers that do that for you.

If a package is lost during transport, it will be resent, and if damaged, will be corrected/sent again. assuming you are using TCP/IP protocol , your transport layer guarantees that data will transfer properly, without you having to deal with it.

(this is a file and not a streaming video, UDP protocol will have possible corruption of data, which is ok in video/audio)

*Just to clear things up: you are at the application layer. Example of layers

Edit:

From Wikipedia regarding TCP/IP:

This abstraction also allows upper layers to provide services that the lower layers do not provide. While the original OSI model was extended to include connectionless services (OSIRM CL),[16] IP is not designed to be reliable and is a best effort delivery protocol. This means that all transport layer implementations must choose whether or how to provide reliability. UDP provides data integrity via a checksum but does not guarantee delivery; TCP provides both data integrity and delivery guarantee by retransmitting until the receiver acknowledges the reception of the packet.

Upvotes: 1

ígor
ígor

Reputation: 1164

You should calculate checksum of file, to validate it on client.

string checkSum=null;
using (System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create()) {
  checkSum= BitConverter.ToString(
    md5.ComputeHash(Encoding.UTF8.GetBytes(theString))
  ).Replace("-", String.Empty);
}

Upvotes: 1

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