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We'll learn about the DateTime struct and parse date values from our CSV file.
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Let's start by creating our class first.
0:01
We'll right-click on the project
choose Add > Class and
0:03
we'll name it GameResult.
0:09
Let's open up our CSV file and
check out the data.
0:12
Our first field is GameDate.
0:17
It's got both a date and
a time in the field.
0:20
We can use a date time in C# to
represent this date and time.
0:23
Let's make the class public and
0:29
public DateTime GameDate, get, set.
0:34
A date time in C# is a struct,
we mentioned structs before,
0:43
let's talk a little more about them
before we get into using DateTime.
0:47
Earlier we said that a struct
is a lot like a class, but
0:51
it has some limitations, but
it also has some advantages.
0:54
A struct takes up less
memory than a class and
0:58
its members are usually
very closely related.
1:01
There are a few case in which you
might want to create one yourself but
1:04
it's not very common in
everyday development.
1:08
However, it's important to know
the differences between a struct and
1:10
a class for when you happen
upon them in your projects.
1:14
A struct is a value type.
1:17
The other value types in C# are ones we've
been using, integers, booleans, and bytes.
1:19
Here's a table that lists
all the value types in C#.
1:26
Here's our struct.
1:33
In C#, we've also got reference types.
1:35
When we create an object from a class,
that object is a reference type.
1:38
The big difference
between a value type and
1:44
a reference type is about
how it's stored in memory.
1:46
When we create an object from a class and
assign it to a variable,
1:50
the variable holds the reference to
the object and not the object itself.
1:54
It's like an address.
1:59
I can write down the address of a house
on multiple pieces of paper, but
2:01
the piece of paper doesn't
hold the actual house.
2:05
It tells us where the house is located.
2:08
We can create multiple variables and
assign them to the same object, but
2:11
there's only one copy of that
object stored in memory.
2:15
And all the variables only hold
a reference to that one object.
2:19
But when we create a value type,
it doesn't hold a reference,
2:23
it holds the actual value.
2:27
If we create multiple variables and
2:30
assign them to a value type, each of those
variables will hold a copy of the value we
2:32
assign our date time struct
represents a single point in time.
2:36
It has a static property on it that
you'll use quite often as a developer,
2:42
DateTime now.
2:47
Let's check it out in
the C# interactive window.
2:48
View > Other Windows > C# Interactive.
2:51
DateTime.Now.
2:57
DateTim.Now returns a DateTime object
that represents the point in time it was
3:03
assigned, according to the system
that the application is running on.
3:07
The DateTime object itself has some
helpful properties, that lets us access
3:12
components of the date and time like
hour or minute or even day of the week.
3:17
DataTime.Now.DayOfWeek.
3:21
We need to parse the game date field in
our CSV file into a DateTime object so
3:28
we can store it in our game result class.
3:32
Let's do that inside our
read soccerResults method.
3:35
The first line of our file contains the
header values from our spreadsheet, but
3:41
we don't really need that.
3:45
Before our while loop here, we can read
the first line to sort of throw it away
3:47
for now, reader.ReadLine,
then the position of the reader
3:52
in the file will be at our first line of
data, which is what we really care about.
3:58
Let's instantiate a new GameResult.
4:03
var gameResult = new
4:05
GameResult Now we can assign a value
4:10
to our gameDate property, but we'll
need to convert it to a date-time first.
4:17
The date-time struct has
a method on it called parse.
4:22
We can call it on the first element of our
values array, which is the gameDate value.
4:27
gameResult.GameDate =
4:31
DateTime.Parse values,
first one in the array.
4:39
But what would happen if the value in
the array element wasn't a valid date like
4:51
if it were null or in the wrong format?
4:55
We would get an exception.
4:58
We could add a block here to
make sure it's handled, but
5:00
there's a better way to parse the string
into a DateTime with the try parse method.
5:04
DateTime.TryParse values,
5:09
First one in the array and
we need an out parameter gameDate.
5:17
The TryParse method returns a boolean
value if the parse was successful.
5:25
And it takes two parameters
the string to parse and
5:29
a DateTime value that will hold
the result of the parse operation.
5:32
The out keyword here is indicating that
the value was passed as a reference.
5:36
Since the DateTime type is a value type,
5:41
we're indicating that it should
be passed as a reference.
5:44
When you pass a value type
into a method without it,
5:47
it creates a copy of the value.
5:50
We need to declare the DateTime
variable though, to hold the value.
5:53
Date time gameDate,
5:58
then we can add an if statement around the
TryParse, and if the parse was successful,
6:03
well, we'll assign the game date value
to the property in our game result.
6:07
If, TryParse is successful,
6:12
then the gameResult .GameDate
gets the game date value.
6:18
And we can delete this line here.
6:27
And so, if the TryParse isn't successful
our program will just skip it.
6:30
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