SHA1 hash question

I have this method to hash a string:

 byte[] buffer = enc.GetBytes(text);
 SHA1CryptoServiceProvider cryptoTransformSHA1 =
                new SHA1CryptoServiceProvider();
 string hash = BitConverter.ToString(
                cryptoTransformSHA1.ComputeHash(buffer)).Replace("-", "");

 return hash;

My question is:

Is the resulting hash always开发者_如何转开发 the same for the same string?

I hashed a string a couple of days ago and it seems that it now resulted in another hash, but i'm not sure.

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Yes, the same plaintext string will hash to the same SHA1 hash every time.

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As long as the bytes are the same, you will end up with exactly the same hash. Note that special characters and whitespace are bytes as well.

Wikipedia Link

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Id depends! The same plain text string will hash to the same SHA1 hash if you use the same Encoding! Using different Encoding will result in different SHA1 hash.