c# - 检查字符串是否采用特定日期格式

Question

您好，我收到了一个日期格式为 yyyy-MM-dd 的字符串，但我想将其与 dd-MM-yyyy 格式进行比较，以防万一它不一样，肯定不一样，我想转换它，对我来说问题不是转换，而是比较两种格式......所以我想也许是这样的

var dt = obj.date; //this a string

if (dt.formatDateorsomethingIguess == "dd/MM/yyyy") //this is the part I'm asking for
{
     usedt(dt);
} 
else 
{
    DateTime dt_format = DateTime.ParseExact(dt.Trim(), "dd-MM-yyyy",
    System.Globalization.CultureInfo.InvariantCulture);
    usedt(dt_format);
}

Answer 1

您可以通过几次调用 TryParseExact 来解决此问题:

public static DateTime ParseDate(string input)
{
    DateTime result;

    if (DateTime.TryParseExact(input, "yyyy-MM-dd", CultureInfo.CurrentCulture, DateTimeStyles.None, out result)) return result;
    if (DateTime.TryParseExact(input, "dd-MM-yyyy", CultureInfo.CurrentCulture, DateTimeStyles.None, out result)) return result;

    throw new FormatException();
}

快速测试一下:

public static void Main()
{
    string[] tests = new string[] { "2018-06-29", "29-06-2018","Invalid" };

    foreach (var t in tests)
    {
        var result = ParseDate(t);
        Console.WriteLine( "Year: {0}  Month: {1}  Day: {2}", result.Year, result.Month, result.Day );
    }
}

输出:

Year: 2018  Month: 6  Day: 29
Year: 2018  Month: 6  Day: 29
Run-time exception (line 18): One of the identified items was in an invalid format.

Sample code on DotNetFiddle