.net vs Objective c SHA 512 mismatch

I am trying to write function for creating sha512 string in objective from .net function which is 

public static string GetSHA512(string strPlain)
{
    UnicodeEncoding UE = new UnicodeEncoding();
    byte[] HashValue = null;
    byte[] MessageBytes = UE.GetBytes(strPlain);
    System.Security.Cryptography.SHA512Managed SHhash = new System.Security.Cryptography.SHA512Managed();
    string strHex = string.Empty;

    HashValue = SHhash.ComputeHash(MessageBytes);
    foreach (byte b in HashValue)
    {
        strHex += String.Format("{0:x2}", b);
    }
    return strHex;
}

This gives result as 

input : pass123
output: 2a6353744cc2914c602265f50d2e413d0561368775756392517abb340ef75d52ee0c5d3623ddd1826fd768a13dca8961f5957c75df0d793b9d7537aabe050705

What I have tried is as follow

-(NSString *)createSHA512:(NSString *)string
{
    const char *cstr = [string cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:string.length];
    uint8_t digest[CC_SHA512_DIGEST_LENGTH];
    CC_SHA512(data.bytes, data.length, digest);
    NSMutableString* output = [NSMutableString  stringWithCapacity:CC_SHA512_DIGEST_LENGTH];

    for(int i = 0; i < CC_SHA512_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x", digest[i]];
    return output;
}

which gives result below

input : pass123
output: fd37ca5ca8763ae077a5e9740212319591603c42a08a60dcc91d12e7e457b024f6bdfdc10cdc1383e1602ff2092b4bc1bb8cac9306a9965eb352435f5dfe8bb0

Can anyone please suggest what am I doing wrong ?

Why these two values differ ?

Please correct my mistakes.

EDIT

Mean While I have tried changing encoding to NSUTF16StringEncoding and NSUnicodeStringEncoding which results still different and as follows

input : pass123
output: 514331e3f7ca0a295539347ebccc4e4f095fe5f3c1df10d43b4d550144c7b30ba9507831893ea63ea22e62e993be529b0d14be7800a90aa0de199d6be62a5f1b
Jon Skeet
people
quotationmark

In the Objective C version you're converting the text to binary using UTF-8. In the .NET version you're using UTF-16. That may not be the only difference, but it's certainly a relevant one.

I'd rewrite your .NET method as:

public static string GetSHA512(string text)
{
    byte[] messageBytes = Encoding.UTF8.GetBytes(text);

    byte[] hash;
    using (SHA512 hashAlgorithm = SHA512.Create())
    {
        hash = hashAlgorithm.ComputeHash(messageBytes);
    }

    StringBuilder builder = new StringBuilder();
    foreach (byte b in hash)
    {
        builder.AppendFormat("{0:x2}", b);
    }        
    return builder.ToString();
}

people

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