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In this lecture, we will be dealing with exceptions and also we will fix a minor bug.



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We will be using try and catch blocks in order to deal with the exceptions and the minor bug is in case



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the given command doesn't contains any space character our parser will throw an error.



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We will be fixing it by using an if statement.



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And also, if any exceptions occur, you will be returning the message as string, the error message as string,



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this information will be used for determining why our command didn't work.



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If you are new to these concepts, please learn try and catch blocks before keeping continue.



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So let's start coding.



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Inside the operations class



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we will be using try and catch blocks in all of the functions.



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Let's start with download file function.



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Encapsulate all of your code inside try block



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and catch any possible exception by using catch statement, catch block.



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In order to get the error message, we will be using an instance of the exception class.



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Let's call it e and in order to return the error message, we will be using the message property of



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the exception class and we need to convert its data type to string.



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So we will be using the tostring method.



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Since we are returning a string, we need to change return that type of the function, it will be



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string and also we need to create a success message.



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Let's call it "file has been downloaded" and append savepath next to it.



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Do the same thing for all of the functions.



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Encapsulate your code inside try block and catch any possible exception using catch block.



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And create the success message.



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And also, we need to change the return data type of the function, it will be string.



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And for enumworkingdirectory function, use try block and encapsulate all of your code inside



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try block and catch any possible exception using the catch block.



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And lastly, the executecmd function.



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Use try block



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and



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catch any possible exception using catch block.



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So we are done with dealing with exceptions.



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Let's fix our minor bug.



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Go back to your commandparser function.



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If the given command



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doesn't contain any space character, this split function will throw an error.



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To fix this situation, we will be using an if statement if the given command contains any space character



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we will be performing split operations else



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We will be initializing the value of the command as cmd variable's itself.



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So let's perform split operations inside the if block



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and



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let's initialize the first value of the command variable and argument variable as empty strings.



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So if the given command contains the space character



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We will be changing their values according to the split functions.



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And in case the cmd variable does not contain any space character, we will be initializing



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the value of the command as the cmd variable's itself and argument will be empty.



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So we have completed our tasks.



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Let's test our code. Go back to your program.cs



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and call commandparser function.



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Let's use the ls command with argument as nonexistent directory.



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Let's call it C:\Windowssse and let's see let's see the error message.



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Oops, there's an error exists, let's fix that first, where is the error?



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Oh we need to use the return function.



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Lets try it again.



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As you can see, the error message has been returned,  "could not find a part of the path" and let's



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try to call enumworkingdirectory function with a valid path.



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Let's see.



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Yep, it worked.



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As you can see, we have listed all of the files and folders under the C:\Windows directory.



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One more improvement can be performed here.



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If the given command only contains the ls keyword, we need to enumerate our current working directly



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to do so, go back to your enumworkingdirectory function



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and if the given path is empty



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If give given path is empty, intiliazie it's value as our current working directory to do so, we will



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be using an instance of the general info class.



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An instance it is an instance of the general info class and we will be using cdirectory variable,



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this variable holds our current directory information.



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So if the given path is empty, we will be using our current working directory as given path.



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Let's test or code.



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Yep, perfect, as you can see, we have listed files and folders under our current working directory,



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so that's it for this lecture.



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See you in the next one.