C# 문자열 Mid,Left,Right

public string Mid(string sString, int nStart, int nLength)
{
string sReturn;

--nStart;

if (nStart <= sString.Length)
{
if ((nStart + nLength) <= sString.Length)
{
sReturn = sString.Substring(nStart, nLength);
}
else
{
sReturn = sString.Substring(nStart);
}

}
else
{
sReturn = string.Empty;
}

return sReturn;
}
public string Left(string sString, int nLength)
{
string sReturn;

if ( nLength > sString.Length )
{
nLength = sString.Length;
}

sReturn = sString.Substring(0, nLength);

return sReturn;
}
public string Right(string sString, int nLength)
{
string sReturn;
if (nLength > sString.Length)
{
nLength = sString.Length;
}
sReturn = sString.Substring(sString.Length - nLength,nLength);

return sReturn;
}