public virtual unsafe int LastIndexOf(string source, char value, int startIndex, int count, CompareOptions options)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
if ((((options & ~(CompareOptions.IgnoreWidth | CompareOptions.IgnoreKanaType | CompareOptions.IgnoreSymbols | CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase)) != CompareOptions.None) && (options != CompareOptions.Ordinal)) && (options != CompareOptions.OrdinalIgnoreCase))
{
throw new ArgumentException(Environment.GetResourceString("Argument_InvalidFlag"), "options");
}
if ((source.Length == 0) && ((startIndex == -1) || (startIndex == 0)))
{
return(-1);
}
if ((startIndex < 0) || (startIndex > source.Length))
{
throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
}
if (startIndex == source.Length)
{
startIndex--;
if (count > 0)
{
count--;
}
}
if ((count < 0) || (((startIndex - count) + 1) < 0))
{
throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_Count"));
}
if (options == CompareOptions.OrdinalIgnoreCase)
{
return(TextInfo.nativeLastIndexOfCharOrdinalIgnoreCase(TextInfo.InvariantNativeTextInfo, source, value, startIndex, count));
}
if (!this.IsSynthetic)
{
return(LastIndexOfChar(this.m_pSortingTable, this.m_sortingLCID, source, value, startIndex, count, (int)options));
}
if (options == CompareOptions.Ordinal)
{
return(LastIndexOfChar(CultureInfo.InvariantCulture.CompareInfo.m_pSortingTable, this.m_sortingLCID, source, value, startIndex, count, (int)options));
}
return(this.SyntheticLastIndexOf(source, new string(value, 1), startIndex, count, GetNativeCompareFlags(options)));
}