public int LastIndexOf(string value, int startIndex, int count, StringComparison comparisonType)
{
if (value == null)
{
throw new ArgumentNullException(nameof(value));
}
// Special case for 0 length input strings
if (this.Length == 0 && (startIndex == -1 || startIndex == 0))
{
return((value.Length == 0) ? 0 : -1);
}
// Now after handling empty strings, make sure we're not out of range
if (startIndex < 0 || startIndex > this.Length)
{
throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
}
// Make sure that we allow startIndex == this.Length
if (startIndex == this.Length)
{
startIndex--;
if (count > 0)
{
count--;
}
}
// 2nd half of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
if (count < 0 || startIndex - count + 1 < 0)
{
throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
}
// If we are looking for nothing, just return startIndex
if (value.Length == 0)
{
return(startIndex);
}
switch (comparisonType)
{
case StringComparison.CurrentCulture:
case StringComparison.CurrentCultureIgnoreCase:
return(CultureInfo.CurrentCulture.CompareInfo.LastIndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType)));
case StringComparison.InvariantCulture:
case StringComparison.InvariantCultureIgnoreCase:
return(CompareInfo.Invariant.LastIndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType)));
case StringComparison.Ordinal:
case StringComparison.OrdinalIgnoreCase:
return(CompareInfo.LastIndexOfOrdinal(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType) != CompareOptions.None));
default:
throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
}
}
