public int IndexOf(string value, int startIndex, int count, StringComparison comparisonType)
{
// Validate inputs
if (value == null)
{
throw new ArgumentNullException(nameof(value));
}
if (startIndex < 0 || startIndex > this.Length)
{
throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
}
if (count < 0 || startIndex > this.Length - count)
{
throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
}
if (comparisonType == StringComparison.Ordinal)
{
int result = SpanHelpers.IndexOf(
ref Unsafe.Add(ref this._firstChar, startIndex),
count,
ref value._firstChar,
value.Length);
return((result >= 0 ? startIndex : 0) + result);
}
switch (comparisonType)
{
case StringComparison.CurrentCulture:
case StringComparison.CurrentCultureIgnoreCase:
return(CultureInfo.CurrentCulture.CompareInfo.IndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType)));
case StringComparison.InvariantCulture:
case StringComparison.InvariantCultureIgnoreCase:
return(CompareInfo.Invariant.IndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType)));
case StringComparison.OrdinalIgnoreCase:
return(CompareInfo.IndexOfOrdinal(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType) != CompareOptions.None));
default:
throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
}
}
