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c#design-patternsgenericsif-statementswitch-statement
Masoud
Masoud

Reputation: 8171

Avoid if-else or switch-case statements for deciding

I'm developing a generic search form, that search controls in that form are depends on type of <T>properties, for example if T is Order, 

public class Order
{
   public string OrderNumber {get; set;} // search control is 1 TextBox
   public decimal OrderWeight {get; set;} // search controls are 2 TextBox (for accepting a range)
}

the search form will be something like this

enter image description here

i used this statements in my form for deciding that what are appropriate controls for each T property:

if (propertyType.Name == "System.String")
   InsertOneTextBox(paramInfo);
else 
   if(propertyType.Name == "System.Int32" || propertyType.Name == "System.Decimal") 
      InsertTwoTextBoxs(paramInfo);
   else
    if(propertyType.Name == "System.DateTime") 
      InsertTwoDateTimePickers(paramInfo);
    else
       if(propertyType.Name == someotherconditions)    
          InsertOneComboBox(paramInfo);
   ....

is there any best practice for avoid using if elses or switch case for deciding that what are appropriate controls set for each property type?

Upvotes: 2

Views: 1250

Answers (2)

JustCode
JustCode

Reputation: 312

Create a class using TinyType and make your input string strong typed. Based on these inputs create 4 strategies ( Talking about Strategy Pattern) all driving from same interface. Create a Factory class and inject in your class where you need these strategies. Now inject this factory in your class let your stringtyped input and factory decide what kind of insertion you want to do ( one text box/ 2 text box etc.)

Upvotes: 0

Dennis
Dennis

Reputation: 37770

You can build some kind of map:

Upd.

According to your comment:

    // somewhere this class is defined in your code
    class ParamInfo {}

    private readonly Dictionary<Type, Action<ParamInfo>> typeToControlsInsertActionMap;

    public MyForm()
    {
        typeToControlsInsertActionMap = new Dictionary<Type, Action<ParamInfo>>
        {
            { typeof(string), InsertOneTextBox },
            { typeof(int), InsertTwoTextBoxs },
            { typeof(decimal), InsertTwoTextBoxs },

            // etc.
        };
    }

    private void InsertOneTextBox(ParamInfo paramInfo) {}
    private void InsertTwoTextBoxs(ParamInfo paramInfo) {}

Here Action<ParamInfo> is a delegate, which inserts appropriate controls, depending on property type:

var paramInfo = // ...
var propertyType = // ...    

typeToControlsInsertActionMap[propertyType](paramInfo);

Note, that you shouldn't check type name in your case. Use typeof operator instead.

Upvotes: 5

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