Question

This is the Delphi code I’m trying to convert to .net:

   s1 := Copy ( s1 , 1,x - 1) + Copy(s1, x + 1,Length(s1));

I tried:

  s1 = s1.Substring(x - 1, 1) + s1.Substring(s1.Length, x + 1)

But I get error’s when the index is out of range. in Delphi it works fine.

Added one line to convert..
s2 := s2 + chr(3);

Answer 1

Your parameters to Substring are reversed–the start index comes first just as in Delphi.

Delphi string indexing is 1-based. The .net string indexing is 0-based. You have the classic off-by-one error.

Finally, you cannot play so loose with the length parameter to Substring. In Delphi’s Copy you can specify an arbitrarily large length value and you will get all the right-most characters. In Substring you must not ask for more characters than there are. If you do then ArgumentOutOfRangeException is thrown.

You need this:

s1 = s1.Substring(0, x-1) + s1.Substring(x, s1.Length-x)

I’m assuming you have already ensured that x is in the range 0 to s1.Length-1.

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As for your additional question,

s2 := s2 + chr(3);

translates to

s2 = s2 + Chr(3)