DateTime.TryParse中的奇怪行为

我理解您的观点并调试点网框架代码以了解后台发生的情况。

TryParse方法将忽略DateTimeStyles.AssumeLocal标志，并且仅AdjustToUniversal处理标志。

if ((styles & DateTimeStyles.AdjustToUniversal) != 0) {
            return (AdjustTimeZoneToUniversal(ref result));
        }
        return (AdjustTimeZoneToLocal(ref result, bTimeOnly));

另一方面，TryParseExact方法已正确实现，并且具有处理DateTimeStyles.AssumeLocal标志所需的所有逻辑。查看此实现中如何处理其他情况。

            // If AssumeLocal or AssumeLocal is used, there will always be a kind specified. As in the
            // case when a time zone is present, it will default to being local unless AdjustToUniversal
            // is present. These comparisons determine whether setting the kind is sufficient, or if a
            // time zone adjustment is required. For consistentcy with the rest of parsing, it is desirable
            // to fall through to the Adjust methods below, so that there is consist handling of boundary
            // cases like wrapping around on time-only dates and temporarily allowing an adjusted date
            // to exceed DateTime.MaxValue
            if ((styles & DateTimeStyles.AssumeLocal) != 0) {
                if ((styles & DateTimeStyles.AdjustToUniversal) != 0) {
                    result.flags |= ParseFlags.TimeZoneUsed;
                    result.timeZoneOffset = TimeZoneInfo.GetLocalUtcOffset(result.parsedDate, TimeZoneInfoOptions.NoThrowOnInvalidTime);
                }
                else {
                    result.parsedDate = DateTime.SpecifyKind(result.parsedDate, DateTimeKind.Local);
                    return true;
                }
            }
            else if ((styles & DateTimeStyles.AssumeUniversal) != 0) {
                if ((styles & DateTimeStyles.AdjustToUniversal) != 0) {
                    result.parsedDate = DateTime.SpecifyKind(result.parsedDate, DateTimeKind.Utc);
                    return true;
                }
                else {
                    result.flags |= ParseFlags.TimeZoneUsed;
                    result.timeZoneOffset = TimeSpan.Zero;
                }
            }
            else {
                // No time zone and no Assume flags, so DateTimeKind.Unspecified is fine
                Contract.Assert(result.parsedDate.Kind == DateTimeKind.Unspecified, "result.parsedDate.Kind == DateTimeKind.Unspecified");
                return true;
            }

附带说明，调试Dot Net框架代码很有趣。如果您有兴趣，请从这里开始。