Even better, make it an Extension method to the string class.

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>Can be optimized in that case
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>would be like this
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>public static string ChrTran(this string s, string[]  from, string[] to)
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>Of course - the length of the arrays from and to must be equal
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>It's an extra loop. sb needs to be instantiated only once, and only once sb.ToString();
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>Also, in the oiginal code above from and to are not checked for null values