Part 54 C# Tutorial Reflection Example Video Lecture | C sharp: Enhance your Skills (English) - Back-End Programming

hello welcome to presume technologies
I'm ranked it this is Pat fifty-four
reflection example in this session we'll
look at a practical example of using
reflection if you haven't watched part
53 where we have covered reflection
basics I would strongly encourage you to
watch that video first before continuing
with the session now in this session
what I want to do is basically develop a
simple Windows application
you know if you can see a form here the
users will enter the name of the type
for example system not strength or
system got in 32 or system don't console
class when they enter the name of the
class here you know they need to enter
the name once they do that and when they
click this button discovered type
information now I want to list all of
the methods in that class and all of the
properties and constructors in their
respect to list boxes as shown here and
to do this it's pretty simple if you
have got what we have discussed in the
previous session it's very very simple
to do that and let's quickly see how to
do it if you look at this one I already
have a windows forms application created
here and I have created a form which has
got a textbox label a button control and
then three list boxes and then when I
click this button that's when we need to
inspect the type information and
populate the respective list boxes let's
see have to do that okay we know that
the class is related to reflection are
present in system reflection namespace
so let's improve that fast so system dot
reflection now what we want to do is
when users run this application they
enter the name of the type into this
text box and if you look at the ID of
that text box it's because the
properties it it is text
typename okay so we need to take the
name of the type from this text box and
then find the type information and
populate these list boxes so let's see
how to do that so string type name is
equal to so users will enter the type
name in that text box so let's get that
from the text box once we do that we can
use the type classes get type static
method now we have covered the basics of
this in the previous session so please
watch the previous session if you
haven't already done so so we get the
type here and once we have the type you
know what to do it's pretty simple from
here so type T so we got the type here
and now what we need to do we need to
get methods properties and constructors
and it's pretty simple so all you do is
T dot get methods and you know get
methods will return method info we have
seen that in the previous session again
method info array so method info array
and we call this let's say methods is
equal to that and what we need to do we
need to use a for each loop so for each
method in for and let's say method n
it's collection what we need to do in
this forum we have this list methods
list box so we need to add that method
information to that list box so LST
methods to the list box but items
because it's the items collection dot
add what we need to add the name of the
method so I take the method object and
then say method dot name so now if we
just run it as these so what's happening
here we need to enter the type name
let's say system dot console class so we
know the console class present in system
namespace when I say discover type
information we have an error here let's
see what is that error okay continue
let's see let's put a breakpoint and see
why are we getting that error so when we
run this now so system dot console class
and as Welli console and we click the
button discover type information let's
say that okay so so type is null for
some reason so let's understand why is
that type now because we are saying type
would get type and this is why instead
of passing the variable name we
hard-coded that as a string okay so
that's a mistake so stop that it's a
copy-paste error plus in the type name
instead of passing it as strain within
double quotes so now we run that an
intersystem don't console class system
console class so disco type information
you see that we get all the methods
within the console class for example we
have write line now write line is an
overloaded function so that's why you
see it so many times let's say I want
the return type of the function as well
within this list all you need to do is
along with the method
maybe I want the return types method not
return type dot name and then you give a
space and then all right so now when we
run this we should get the return type
of the method as well so system console
and discover type information and you
should see the return type of every
method and obviously for console dot
write line it's void so void write line
and for read line it would be string so
you should see for read line at a string
okay similarly if you want you know on
the second list box we want to show
properties and on the third one
constructors to do that it's a simple
copy-paste except that you will replace
method I mean instead of get methods
what you will specify is get what's the
second one we want properties will say
get properties so T dot get properties
and get properties will return property
info array so instead of method info we
will say property info and this is
extremely easy once you know how to get
one specific you know set of methods of
properties it's extremely easy for the
other types it's just the names are
different property info and this is
going to be property and this collection
is properties and what we need to do
instead of populating the list of
methods list box it will be list
properties list box
so list properties note items to add
what we want a property will also have a
return type so property dot I think its
property type so if you're not sure just
hit the dot you know and you can
daintily sense will show you different
properties and methods and when you
highlight here look at that property
type gets the type of this property okay
so I mean after you get the basics of
dotnet it's it's mostly self learning
you can learn advice yourself with the
help of it in trial and intellisense so
dot name and then what else I want I
want the name of the property as well so
property name that's it
so now if we run that we should get
properties is well let's do it for
constructors and then we will run it all
at once
so for constructors we use P dot get
constructors method and the constructor
is constructed in four and we will give
the variable s constructors and for each
constructor info object let's call this
constructor in constructors collection
what we want to do and in the from the
previous page session if you remember a
constructor dot name you know we know
that a constructor will have the same
name as that of the class so constructed
or name will be of no use so instead of
that when I say constructor door to
string the to string method is
overridden to give us you know what are
the parameters that the constructor
takes am which is useful so instead of
all this for a constructor
all we do is constructor dot to strength
okay so now if we run this and by the
way there's one more thing it's not list
properties the list box is list
constructors so list constructors that
items to add so now when we run this and
maybe we give let's say system dot
string string class discover type
information look at that it's got two
properties
you know this many constructors in these
many methods and similarly if you want
you know there is something called
system or text or string builder class
they say discover type information look
at that it has got so many and I think
it's actually adding all this when we
have got a slight problem here which we
will create now systems at console when
I say discover type information system
dot console doesn't have an entity tool
properly I mean length property so where
is this coming from the previous values
are being retained in this list box and
to correct that all you do is set them
to empty whenever we start so list item
list methods items that clear the items
and do the same thing with the other
list
so we have list properties list
properties and list constructors just
clear them before you start adding
anything so now if we run it should do
so system dot may be text dot
stringbuilder
discover type information we get that on
the other hand when we go back to system
dot console so this type information
alright so it's working as expected now
so it's a pretty simple example way we
are able to discover the type
information at runtime and populate
these list boxes and remember with this
you know you can with reflection it's
not just that listing methods properties
or constructors there are variety of
things that you can do for example when
you say t dot there are several you know
boolean properties as well he's the type
abstract is it an array you know there
are several properties and methods that
are really really useful for variety of
things okay
now whenever you have time just explore
the system reflection namespace it's
really useful alright so on this slide
you can find some resources for a speed
or net and c-sharp interview questions
that's it for today thank you for
listening have a great day