CODEWITHSUNDEEP
c#datetimeoffset
user11131551
user11131551

Reputation:

How do I get the value month of Datetimeoffset?

I have a list of data that have datetimeoffset? as a column inside. I want to get specific data that has the month I want but don't know how. Below are those code I have tried.

This return me with error of No overload for method 'Tostring' which is weird since I can pass datetimeoffset? and use it in other function but if I do it directly inside where I get it, I can't use it.

      int d = DateTime.Now.Month;
      string f = d.ToString();
      var s = _dbContext.Documents.FirstOrDefault(x => x.ApplyDate.ToString("MM") == f);
      return Json(s);

This return null

      int d = DateTime.Now.Month;
      string f = d.ToString();
      var s = _dbContext.Documents.FirstOrDefault(x => x.ApplyDate.Value.ToString("MM") == f);
      return Json(s);

Upvotes: 2

Views: 1666

Answers (3)

Transformer
Transformer

Reputation: 7429

Your code above shows DateTime, not DateTimeOffSet.

DateTimeOffSet is Struct, and if you have a nullable value, you need to check the value first and then get the month from the value part

DateTimeOffSet myNullableDateTime = someValue...//

Option 1:

// notice I added value below

myNullableDateTime.HasValue? "?Month="+myNullableDateTime.EscapeDataString(myNullableDateTime.Value.ToString()):"")

Option 2:

if(myNullableDateTime.HasValue)
 {
    var Month = myNullableDateTime.Month
    TimeSpan difference = DateTimeOffset.Now.Subtract(myNullableDateTime.Value);
    // convert the difference to what you need and get Month 
 }

I have not compiled it, but it should get you the answer or pretty close.

Upvotes: 0

styx
styx

Reputation: 1917

DateTimeOffset? is Nullable type therefore is has no overload of ToString(string format) like DateTimeOffset has.

to get get the month value from your DateTimeOffset? you can

  1. x.ApplyDate.Value.ToString("MM")
  2. x.ApplyDate.Value.Month

please consider that you might want to check if ApplyDate.Value is null before obtaining its Month property

Upvotes: 0

Frederik Gheysels
Frederik Gheysels

Reputation: 56934

You can retrieve the month of a nullable datetimeoffset like this:

DateTimeOffset? dt;
dt?.Value.Month;

However, I really wonder if EF will be able to translate this:

x => x.ApplyDate?.Month == f

into a SQL expression. I presume that it will fallback to in-memory filtering. Next to that, even if EF is able to translate this into a SQL expression, it won't be optimal as indexes that might be defined on that column will not be used.

Therefore, I'd suggest to rewrite your LINQ expression to something like this:

x :> x.ApplyDate != null && x.ApplyDate >= new DateTimeOffset(someDate.Year, someDate.Month, 1) && x.ApplyDate <= new DateTimeOffset(someDate.Year, someDate.Month, daysInMonth)

(Given you want to retrieve the data that belong to a specific month in a specific year. If you want to retrieve records that belong to a certain month, regardless the year, I see no other option)

Upvotes: 2

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