- Inheritance 3:35
- Inheritance in Code 5:27
- Inheritance 5 questions
- Inheritance 1 objective
- Catching Exceptions in C#
- Throwing Exceptions 4:49
- Throwing Exceptions 1 objective
- Catching Exceptions 1 objective
- Exception Messages 3:02
- Custom Exceptions 6:23
- Custom Exceptions 2 objectives
- Catching Exceptions 5:02
- Catching Exceptions 6 questions
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Exception Messages
3:02Storing a message in the exception object is one way to add information to the exception.
Exceptions should be used to communicate
about an error that has happened.
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We can then use this information
to instruct the user on
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how to resolve the issue, or
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we may be able to use the information
to try to resolve it on our own.
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Exceptions often happen as
a result of programming mistakes.
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In that case, exceptions are used
to communicate to the programmer
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that there's a bug that needs to be fixed.
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In any case,
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it's best to provide as much information
about what may have caused the problem.
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There are a number of ways we can add
additional information to exceptions.
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One way we can communicate what happened,
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is by passing a message to
the exceptions constructor.
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Most exception types will
allow you to pass a string
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in as one of the constructors parameters.
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We can do that.
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Let's go back to the map location
class and make this change.
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We'll type, x,
y is outside the boundaries of the map.
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Now back in main where we catch this
exception, we can access this message.
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Up until now,
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we haven't needed to have access to the
actual exception object that was created.
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In order to access this message,
we'll need to get this object.
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We do that by declaring a variable for
the exception.
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You can name this variable
whatever you like, but
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conventionally, many coders name it EX.
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Now, that we have an exception object,
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we can use it to access
the message stored inside of it.
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Let's print it to the console
instead of this message.
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Let's run the program again
to see what this looks like.
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There we go.
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Now we've printed out the message
that was inside the exception object.
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In a typical program, there are lots
of ways for errors to occur and
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lots of things can throw exceptions.
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We often want to handle
errors differently,
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based on the type of error that occurred.
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Messages are nice for humans, but
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computer programs rarely have the ability
to read and understand English.
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That's why we have multiple
types of exceptions.
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We've seen some of these
exceptions in previous courses.
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The system.exceptionclass is the most
general purpose exception type.
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Really all it means is
that an error occurred.
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It says nothing about
the type of the error.
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There are more specific types
of exceptions that imply
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that certain types of
errors have occurred.
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For example,
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there's the system.format exception which
is thrown from methods such as ent.parse.
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Which is expecting a string
to have a certain format so
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that it can convert it to an integer.
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System.exception and
system.format exception
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are both exceptions that
are provided by the .net framework.
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We can create our own exceptions though.
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It's as easy as creating a new class.
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Let's take a quick break and
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see how to create our own
exception types in the next video.
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