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Code Smells CSharp

Feature Envy Example

In the Customer class below, the method GetMobilePhoneNumber() provides a North American-formatted mobile Phone number:

public class Phone
{
	private readonly string unformattedNumber;
	public Phone(String unformattedNumber) 
	{
		this.unformattedNumber = unformattedNumber;
	}
	internal string AreaCode
	{
		get 
		{
			return unformattedNumber.Substring(0,3);
		}
	}
	internal string Prefix
	{
		get 
		{
			return unformattedNumber.Substring(3,3);
		}
	}
	internal string Number
	{
		get 
		{
			return unformattedNumber.Substring(6,4);
		}
	}
}
public class Customer…
	private readonly Phone mobilePhone;
	public string MobilePhoneNumber
	{
		get
		{
			return "(" + mobilePhone.AreaCode + ") " + mobilePhone.Prefix + "-" + mobilePhone.Number;
		}
	}
See how Customer reaches into Phone’s data to format the number? Feature Envy often shows up as a misplaced responsibility.
 

public class Phone
{
	private readonly string unformattedNumber;
	public Phone(String unformattedNumber) 
	{
		this.unformattedNumber = unformattedNumber;
	}
	internal string AreaCode
	{
		get 
		{
			return unformattedNumber.Substring(0,3);
		}
	}
	internal string Prefix
	{
		get 
		{
			return unformattedNumber.Substring(3,3);
		}
	}
	internal string Number
	{
		get 
		{
			return unformattedNumber.Substring(6,4);
		}
	}
	public String ToFormattedString()
	{
		return "(" + AreaCode + ") " + Prefix + "-" + Number;
	}	
}
public class Customer…
	private readonly Phone mobilePhone;
	public string MobilePhoneNumber
	{
		get
		{
			return mobilePhone.ToFormattedString();
		}
	}
Now Customer relies on Phone to do the formatting.
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