2012/03/20

string和byte[]的轉換 (C#)

string類型轉成byte[]

byte[] byteArray = System.Text.Encoding.Default.GetBytes ( str );
反過來,byte[]轉成string
string str = System.Text.Encoding.Default.GetString ( byteArray );

其它編碼方式的,如System.Text.UTF8EncodingSystem.Text.UnicodeEncoding class等;例如:
string類型轉成ASCII byte[]:("01" 轉成 byte[] = new byte[]{ 0x30, 0x31}
byte[] byteArray = System.Text.Encoding.ASCII.GetBytes ( str );
ASCII byte[] 轉成string:(byte[] = new byte[]{ 0x30, 0x31} 轉成 "01"
string str = System.Text.Encoding.ASCII.GetString ( byteArray );

有時候還有這樣一些需求:
byte[] 轉成原16進制格式的string,例如0xae00cf, 轉換成 "ae00cf"new byte[]{ 0x30, 0x31}轉成"3031":
        public static string ToHexString ( byte[] bytes ) // 0xae00cf => "AE00CF "
        {
            
string hexString = string.Empty;
            
if ( bytes != null )
            
{
                StringBuilder strB 
= new StringBuilder ();

                
for ( int i = 0; i < bytes.Length; i++ )
                
{
                    strB.Append ( bytes[i].ToString ( 
"X2" ) );
                }

                hexString 
= strB.ToString ();
            }

            
return hexString;
        }

反過來,16進制格式的string 轉成byte[],例如, "ae00cf"轉換成0xae00cf,長度縮減一半;"3031" 轉成new byte[]{ 0x30, 0x31}:
        public static byte[] GetBytes(string hexString, out int discarded)
        
{
            discarded 
= 0;
            
string newString = "";
            
char c;
            
// remove all none A-F, 0-9, characters
            for (int i=0; i<hexString.Length; i++)
            
{
                c 
= hexString[i];
                
if (IsHexDigit(c))
                    newString 
+= c;
                
else
                    discarded
++;
            }

            
// if odd number of characters, discard last character
            if (newString.Length % 2 != 0)
            
{
                discarded
++;
                newString 
= newString.Substring(0, newString.Length-1);
            }


            
int byteLength = newString.Length / 2;
            
byte[] bytes = new byte[byteLength];
            
string hex;
            
int j = 0;
            
for (int i=0; i<bytes.Length; i++)
            
{
                hex 
= new String(new Char[] {newString[j], newString[j+1]});
                bytes[i] 
= HexToByte(hex);
                j 
= j+2;
            }

            
return bytes;
        }


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