C# Generics Help me please

Hi Guys,

Will you help me on my concern? I want to perform code reuse for the snippet below using Generics. How can I turn this to a single method? I am still not that familiar with Generics.

public void ReadInputFiles(string sourcePath)
{
CompanyAddressInputFile path = new CompanyAddressInputFile();
path.Path = sourcePath;
string[] filePaths = GetFiles(path.Path);

foreach (string file in filePaths)
{
CompanyAddressInputFile companyAddressInputFile = new CompanyAddressInputFile();
companyAddressInputFile.Path = sourcePath;
companyAddressInputFile.Filename = Path.GetFileName(file);

ProcessFile(companyAddressInputFile);
}
}

public void ReadOutputFiles(string desPath)
{
CompanyAddressOutputFile path = new CompanyAddressOutputFile();
path.Path = desPath;
string[] filePaths = GetFiles(path.Path);

foreach (string file in filePaths)
{
CompanyAddressOutputFile companyAddressOutputFile = new CompanyAddressOutputFile();
companyAddressOutputFile.Path = desPath;
companyAddressOutputFile.Filename = Path.GetFileName(file);
UpdateAddress(companyAddressOutputFile);
}
}

And, is below a good Generics method implementation?

public string[] GetFiles(T filePath)
{
string[] filePaths = Directory.GetFiles(filePath.ToString());

return filePaths;
}

So as you have started working on re-usability using generics , your code can be converted into something like below (and I found this sort of interesting excercise).

Starting with you classes CompanyAddressOutputFile and CompanyAddressInputFile, as both of the methods ReadInputFiles and ReadOutputFiles are using FileName and Path properties, take them out in base class as below: (Note that if you can bring the logic to one method then instead of having ProcessFile method and UpdateAddress method, try to have one generic/common method that handles these operations and put it on base class -considering it deosn't require any members from the derived classes)

public class BaseCompanyAddressFile
{
public string Path { get; set; }
public string FileName { get; set; }
public void ProcessFile() where T: BaseCompanyAddressFile
{
// try bringing logic to gether from processFile and updateAddress methods if possible.
Debug.WriteLine($"{typeof(T)}");
}
}
public class CompanyAddressInputFile:BaseCompanyAddressFile
{
//rest of your class implementation
}
public class CompanyAddressOutputFile: BaseCompanyAddressFile
{
//rest of your class implementation
}

Now as you have common code in both the methods (ReadInputFiles and ReadOutputFiles), we can convert your methods into generic method that makes use of either CompanyAddressInputFile class or companyAddressOutputFile (specifying constriants on class that makes it possible ot have this method call of type companyAddressInputFile or companyAddressOutputFile)

// I have changed method name to something common for both type of operations.
public void DoInputOutputFileOperation(string sourcePath) where T: BaseCompanyAddressFile, new()
{
T path = new T(); // create an object of type either companyAddressInputFile or companyAddressOutputFile
path.Path = sourcePath; // both class contains these properties due to common base class
string[] filePaths = path.GetFiles(); // this is an extension method defined on BaseCompanyAddressFile class type.
foreach (string file in filePaths)
{
T CompanyAddressFile = new T();
CompanyAddressFile.Path = sourcePath;
CompanyAddressFile.FileName = CompanyAddressFile.GetFileName();
CompanyAddressFile.ProcessFile();
}
}

Extension methods are something that can be called directly on the type on which extension method is defined.

Go through some basics of extension methods and you will get the idea.

Extension methods reside in public static class and methods needs to be public static.

So, I have created another public static class for the same purpose in the same namespace. This class contains two methods, one returning list of files and another returning filename.

I am not sure about how you implemented the GetFileName method so as of now, I am just returning some dummy values.

So now, when you have an object of type companyAddressInputFile or companyAddressOutputFile ( and both are of type BaseCompanyAddressFile), you can directly do obj.GetFiles() and obj.getFileName() and that would reduce the amount of work you need to do in difference cases. Once you have this extension methods, it works across multiple classes considering that you are importing the namespace required.

public static class FileExtensions
{
public static string[] GetFiles(this BaseCompanyAddressFile obj)
{
return Directory.GetFiles(obj.Path);
}
public static string GetFileName(this BaseCompanyAddressFile obj)
{
// need to implement logic to get file name here
return "Filename";
}
}

and finally to make the call to generic method do something like below:

px.DoInputOutputFileOperation(@"Drive:\TEST"); // this makes a call to generic method with type as companyAddressInputFile (like method ReadInputFiles)
px.DoInputOutputFileOperation(@"Drive:\TEST");// this makes a call to generic method with type as companyAddressOutputFile (like method ReadOutputFiles)

5 Replies

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Tapan Patel9y ago
You're welcome.
Teemee Tang9y ago
Hi Tapan Patel,

Thank you very much for your response. It's a big help.
Tapan Patel9y ago
So as you have started working on re-usability using generics , your code can be converted into something like below (and I found this sort of interesting excercise).

Starting with you classes CompanyAddressOutputFile and CompanyAddressInputFile, as both of the methods ReadInputFiles and ReadOutputFiles are using FileName and Path properties, take them out in base class as below: (Note that if you can bring the logic to one method then instead of having ProcessFile method and UpdateAddress method, try to have one generic/common method that handles these operations and put it on base class -considering it deosn't require any members from the derived classes)
public class BaseCompanyAddressFile
    {
        public string Path { get; set; }
        public string FileName { get; set; }

        public void ProcessFile() where T: BaseCompanyAddressFile
        {
            // try bringing logic to gether from processFile and updateAddress methods if possible.
            Debug.WriteLine($"{typeof(T)}");
        }
    }

    public class CompanyAddressInputFile:BaseCompanyAddressFile
    {
        //rest of your class implementation
    }
    public class CompanyAddressOutputFile: BaseCompanyAddressFile
    {
        //rest of your class implementation
    }
Now as you have common code in both the methods (ReadInputFiles and ReadOutputFiles), we can convert your methods into generic method that makes use of either CompanyAddressInputFile class or companyAddressOutputFile (specifying constriants on class that makes it possible ot have this method call of type companyAddressInputFile or companyAddressOutputFile)
// I have changed method name to something common for both type of operations.
public void DoInputOutputFileOperation(string sourcePath) where T: BaseCompanyAddressFile, new()
       {

           T path = new T(); // create an object of type either companyAddressInputFile or companyAddressOutputFile
           path.Path = sourcePath; // both class contains these properties due to common base class
           string[] filePaths = path.GetFiles(); // this is an extension method defined on BaseCompanyAddressFile class type.
           foreach (string file in filePaths)
           {
               T CompanyAddressFile = new T();
               CompanyAddressFile.Path = sourcePath;
               CompanyAddressFile.FileName = CompanyAddressFile.GetFileName();
               CompanyAddressFile.ProcessFile();

           }
       }
Extension methods are something that can be called directly on the type on which extension method is defined.
Go through some basics of extension methods and you will get the idea.

Extension methods reside in public static class and methods needs to be public static.

So, I have created another public static class for the same purpose in the same namespace. This class contains two methods, one returning list of files and another returning filename.
I am not sure about how you implemented the GetFileName method so as of now, I am just returning some dummy values.

So now, when you have an object of type companyAddressInputFile or companyAddressOutputFile ( and both are of type BaseCompanyAddressFile), you can directly do obj.GetFiles() and obj.getFileName() and that would reduce the amount of work you need to do in difference cases. Once you have this extension methods, it works across multiple classes considering that you are importing the namespace required.
public static class FileExtensions
   {
       public static  string[] GetFiles(this BaseCompanyAddressFile obj)
       {
           return Directory.GetFiles(obj.Path);
       }
       public static string GetFileName(this BaseCompanyAddressFile obj)
       {
           // need to implement logic to get file name here
           return "Filename";
       }

   }
and finally to make the call to generic method do something like below:
px.DoInputOutputFileOperation(@"Drive:\TEST"); // this makes a call to generic method with type as companyAddressInputFile (like method ReadInputFiles)
px.DoInputOutputFileOperation(@"Drive:\TEST");// this makes a call to generic method with type as companyAddressOutputFile (like method ReadOutputFiles)
Teemee Tang9y ago
Hi Nilesh Shah,

Will you give me some practical use of Generics? Can I use Generics in my own custom class with unique properties with other class?
Nilesh Shah9y ago
Hi,

I'm not sure if your current code works or you require us to solve any problem in that code.

But generics are used when we have different classes and we want same operation on them, so that instead of writing methods for each class, we write only one generic.

the code you posted may have implemented generics theoratically but file path is always going to be string, so there is no use of defining generic here.

I suggest you read more on it on MSDN.