将overdueDate从DateTime转换为字符串，格式为dd / mm / yyyy 00:00:00

Question

如何将值 overdueDate 从 DateTime 变量转换为格式为 dd / mm / yyyy 00:00:00

    DateTime overdueDate;
    DateTime today = DateTime.Now; 

    if (today.DayOfWeek == DayOfWeek.Monday)
    {
        overdueDate = today.AddDays(-12);
    }
    else if (today.DayOfWeek == DayOfWeek.Tuesday)
    {
        overdueDate = today.AddDays(-13);
    }
    else if (today.DayOfWeek == DayOfWeek.Wednesday)
    {
        overdueDate = today.AddDays(-7);
    }
    else if (today.DayOfWeek == DayOfWeek.Thursday)
    {
        overdueDate = today.AddDays(-8);
    }
    else if (today.DayOfWeek == DayOfWeek.Friday)
    {
        overdueDate = today.AddDays(-9);
    }
    else if (today.DayOfWeek == DayOfWeek.Saturday)
    {
        overdueDate = today.AddDays(-10);
    }
    else if (today.DayOfWeek == DayOfWeek.Sunday)
    {
        overdueDate = today.AddDays(-11);
    }

Answer 1

由于您只需Date部分时间设置为00:00:00，因此您可以使用DateTime.Date属性并将其格式化为：

string str = overdueDate.Date.ToString("dd/MM/yyy HH:mm:ss");

请参阅：Custom Date and Time Format Strings

您在声明时尚未初始化overdueDate，虽然您在条件中为其分配了一些值，但编译器无法确定是否会为其分配任何值。因此，您会收到错误“使用未分配的局部变量”。只需声明它：

DateTime overdueDate = default(DateTime);

Answer 2

var dateString = overdueDate.ToString("dd/MM/yyyy HH:mm:ss");

为了向您提供更详细的信息，请参考custom date time format strings的文档。

这里需要注意的一点是，ToString可以根据文档列出您可以设想的任何日期。

Answer 3

我不是100％肯定你想要达到的目标，但我相信以下是一种更有效的方法。

DateTime overdueDate = DateTime.Now.AddDays(-7);
while (overdueDate.DayOfWeek != DayOfWeek.Wednesday)
    overdueDate = overdueDate.AddDays(-1);