Enumerators - the correct way to parse an enumerator.

First of all - what are enumerators? You can think for the enumerators as for some kind of constants. They are used to check objects against. Let's say you will have the following dropdown: <asp:DropDownList ID="ddlGender" runat="server"> <asp:ListItem Value="1">Maleasp:ListItem> <asp:ListItem Value="2">Femaleasp:ListItem> <asp:ListItem Value="3">Won't shareasp:ListItem> asp:DropDownList> As you know the genders won't ever change, for code convenience, you may want to define an enumerator to hold them, so you can check against: enum EnumUserGender { Male = 1, Female = 2, Unknown

= 3

}



This way, the Male element of the enumerator will have a value of 1, Female will have a value of 2 and Unknown will have a value of 3.

To check a value against enumerator you may do the following:



int Gender = 1;

if (Gender == EnumUserGender.Male)

{



}



In this case the if will evaluate to true, as the Gender variable has a value of 1.



Now, let's return to our case with the asp:DropDownList, we want to be able to know which asp:ListItem was selected by the user. We don't want to convert the value to int first, but to receive it as a EnumUserGender variable. Let's do this in the SelectedIndex SelectedIndexChanged asp:DropDownList:



protected void ddlGender_SelectedIndexChanged(object sender, EventArgs e)

{

EnumUserGender genderSelected = (EnumUserGender)Enum.Parse(typeof(EnumUserGender), ddlGender.SelectedValue, true);

switch (genderSelected)

{

case EnumUserGender.Male:

Response.Write("Check our cars section!");

break;

case EnumUserGender.Female:

Response.Write("Check our make-up section");

break;

case EnumUserGender.Unknown:

Response.Write("If you want you can check either our cars section or our make-up section");

break;

default:

Response.Write("Sorry, there was an" +

"error, please go back and try again," +

" the error was logged and will be reviewed by our team.");

break;

}

}

}



What we did was to actually Parse the Enum , by using its base class method Parse. It recieves 2 parameters + 1 optional:



Parameter 1 is of type Type, this is the type to which the enumerator will be parsed / converted. In our case we use the typeof, function, passing our enum type as a paramter.

Parameter 2 is of type string, this is the value to be parsed.

Parameter 3 is of type bool, and indicates whether the value passed as a string should match case sensitive. If set to true, you will have insensitive Parse, so "mALe" will be parsed correctly.