How to get rid of if-else chain?

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Hi,

I'm currently working on a Winforms application. I have a database and there are tables on it.

I created a Form that responsible for showing data's coming from this data tables. For this purpose I added a Data Grid View control to this form. I also created an 'enum' to specify which data is shown. The form gets the data from the database and show it in Data Grid View.

But I have some problems about it.

I have a lot of different data to show, and so I have a lot of if-else chain. Like;

C#

if(listType == ListViewTypes.Accounts)
{ 
   //get data from database
} else if(listType == ListViewTypes.Persons)
{ 
  // get data from database
} 
//etc...

Is there any solution about that?

Thank you.

What I have tried:

I think about create a different class to handle this but I also use this if-else chain in that class too.

Posted 3-Oct-17 0:46am

Onur ERYILMAZ

Updated 3-Oct-17 1:38am

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CHill60 5-Oct-17 11:32am

I'm a bit late to the party but noting the solution you have accepted then you might find this article useful Dynamic Method Dispatcher[^]

4 solutions

Solution 1

Use a switch:

C#

switch (listType)
   {
   case ListViewTypes.Accounts:
      ...
      break;
   case ListViewTypes.Persons:
      ...
      break;
...
   default:
      ...
      break;
   }

Posted 3-Oct-17 0:48am

OriginalGriff

Solution 2

Depending on the homogenity of the executed code, you could possibly use a Dictionary of delegates. See, for instance: c# - Dictionary with delegate or switch? - Stack Overflow[^].

Posted 3-Oct-17 1:26am

CPallini

Solution 4

As an alternative to Solution 1 (which is perfectly fine): You could also use a Dictionary to map Delegates to your "ListTypes". I prefer doing this over a switch-statement if the case-statements would become rather long. An example (which uses made up types):

C#

class Program
{
    static void Main(string[] args)
    {
        Demo demo = new Demo();

        string action = "multiplyBy3";
        int input = 1;

        int result = demo.DoSomething(action, input);
    }

    class Demo
    {
        static Dictionary<string, Func<int, int>> Actions = new Dictionary<string, Func<int, int>>()
        {
            { "multiplyBy2", x => x * 2 },
            { "multiplyBy3", x => MultiplyBy3(x) },
        };

        public int DoSomething(string action, int input)
        {
            return Actions[action](input);
        }

        static int MultiplyBy3(int input)
        {
            return input * 3;
        }
    }
}

Posted 3-Oct-17 1:38am

Sascha Lefèvre

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F-ES Sitecore · Accepted Answer · 2017-10-03T01:36:00

You could move the "if" statement to a factory class

public interface IDataHandler
{
    void PopulateGridView(GridView gridView);
}

public class AccountsHandler : IDataHandler
{
    public void PopulateGridView(GridView gridView)
    {
        // populate gridView with accounts
    }
}

public class PersonsHandler : IDataHandler
{
    public void PopulateGridView(GridView gridView)
    {
        // populate gridView with people
    }
}

public class DataHandlerFactory
{
    public IDataHandler GetDataHandler (ListViewTypes types)
    {
        switch(types)
        {
            case ListViewTypes.Accounts:
                return new AccountsHandler();
            case ListViewTypes.Persons:
                return new PersonsHandler();
            default:
                throw new NotImplementedException();
        }
    }
}

usage

DataHandlerFactory f = new DataHandlerFactory();

IDataHandler dh = f.GetDataHandler(types);

dh.PopulateGridView(GridView1);

You could even do something like this to get rid of the switch

public class DataHandlerFactory
{
    private static Dictionary<ListViewTypes, IDataHandler> handlers;

    static DataHandlerFactory()
    {
        handlers = new Dictionary<ListViewTypes, IDataHandler>();

        handlers.Add(ListViewTypes.Accounts, new AccountsHandler());
        handlers.Add(ListViewTypes.Persons, new PersonsHandler());
    }

    public IDataHandler GetDataHandler (ListViewTypes types)
    {
        IDataHandler dh;
            
        if (!handlers.TryGetValue(types, out dh))
        {
            throw new NotImplementedException();
        }

        return dh;

    }
}