string-EndsWith

        // Determines whether a specified string is a suffix of the the current instance.
        //
        // The case-sensitive and culture-sensitive option is set by options,
        // and the default culture is used.
        //        
        [Pure]
        public Boolean EndsWith(String value) {
            return EndsWith(value, StringComparison.CurrentCulture);
        }

//确定指定的字符串是否为当前实例的后缀。

//区分大小写和区域性选项由选项设置，

//并使用默认区域性。

[Pure]
        [System.Security.SecuritySafeCritical]  // auto-generated
        [ComVisible(false)]
        public Boolean EndsWith(String value, StringComparison comparisonType) {
            if( (Object)value == null) {
                throw new ArgumentNullException("value");                                
            }
 
            if( comparisonType < StringComparison.CurrentCulture || comparisonType > StringComparison.OrdinalIgnoreCase) {
                throw new ArgumentException(Environment.GetResourceString("NotSupported_StringComparison"), "comparisonType");
            }
            Contract.EndContractBlock();
 
            if( (Object)this == (Object)value) {
                return true;
            }
 
            if( value.Length == 0) {
                return true;
            }
            
            switch (comparisonType) {
                case StringComparison.CurrentCulture:
                    return CultureInfo.CurrentCulture.CompareInfo.IsSuffix(this, value, CompareOptions.None);
 
                case StringComparison.CurrentCultureIgnoreCase:
                    return CultureInfo.CurrentCulture.CompareInfo.IsSuffix(this, value, CompareOptions.IgnoreCase);
 
                case StringComparison.InvariantCulture:
                    return CultureInfo.InvariantCulture.CompareInfo.IsSuffix(this, value, CompareOptions.None);
 
                case StringComparison.InvariantCultureIgnoreCase:
                    return CultureInfo.InvariantCulture.CompareInfo.IsSuffix(this, value, CompareOptions.IgnoreCase);                    
 
                case StringComparison.Ordinal:
                    return this.Length < value.Length ? false : (nativeCompareOrdinalEx(this, this.Length -value.Length, value, 0, value.Length) == 0);
 
                case StringComparison.OrdinalIgnoreCase:                    
                    return this.Length < value.Length ? false : (TextInfo.CompareOrdinalIgnoreCaseEx(this, this.Length - value.Length, value, 0, value.Length, value.Length) == 0);
 
                default:
                    throw new ArgumentException(Environment.GetResourceString("NotSupported_StringComparison"), "comparisonType");
            }                        
        }
 

[System.Security.SecuritySafeCritical]  // auto-generated
        public unsafe virtual bool IsSuffix(String source, String suffix, CompareOptions options)
        {
            if (source == null || suffix == null) {
                throw new ArgumentNullException((source == null ? "source" : "suffix"),
                    Environment.GetResourceString("ArgumentNull_String"));
            }
            Contract.EndContractBlock();
            int suffixLen = suffix.Length;
 
            if (suffixLen == 0)
            {
                return (true);
            }
 
            if (options == CompareOptions.OrdinalIgnoreCase) {
                return source.EndsWith(suffix, StringComparison.OrdinalIgnoreCase);
            }
 
            if (options == CompareOptions.Ordinal) {
                return source.EndsWith(suffix, StringComparison.Ordinal);
            }
 
            if ((options & ValidIndexMaskOffFlags) != 0) {
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidFlag"), "options");
            }
 
            // to let the sorting DLL do the call optimization in case of Ascii strings, we check if the strings are in Ascii and then send the flag RESERVED_FIND_ASCII_STRING  to 
            // the sorting DLL API SortFindString so sorting DLL don't have to check if the string is Ascii with every call to SortFindString.
            return InternalFindNLSStringEx(
                        m_dataHandle, m_handleOrigin, m_sortName, 
                        GetNativeCompareFlags(options) | Win32Native.FIND_ENDSWITH | ((source.IsAscii() && suffix.IsAscii()) ? RESERVED_FIND_ASCII_STRING : 0),
                        source, source.Length, source.Length - 1, suffix, suffix.Length) >= 0;
        }