Get an enumerated field from a string

问题:

Bit of a strange one this. Please forgive the semi-pseudo code below. I have a list of enumerated values. Let's say for instance, like so:

public enum Types
    {
       foo = 1,
       bar = 2,
       baz = 3
    }

Which would become, respectfully, in the code:

Types.foo
Types.bar
Types.baz

Now I have a drop down list that contains the following List Items:

var li1 = new ListItem() { Key = "foo" Value = "Actual Representation of Foo" }
var li2 = new ListItem() { Key = "bar" Value = "Actual Representation of Bar" }
var li3 = new ListItem() { Key = "baz" Value = "Actual Representation of Baz" }

for the sake of completeness:

dropDownListId.Items.Add(li1); dropDownListId.Items.Add(li2); dropDownListId.Items.Add(li3);

Hope that everyone is still with me. What I want to do is to on the Autopostback is take the string "foo" and convert that to Types.foo - without using a switch (as the enumerated values are generated from a database and may change).

I hope that makes sense? Any idea where to even start?

回答1:

Sure:

Types t;
if(Enum.TryParse(yourString, out t)) // yourString is "foo", for example
{
    // use t
}
else
{
    // yourString does not contain a valid Types value
}

There's also an overload that takes a boolean that allows you to specify case insensitiveness: http://msdn.microsoft.com/en-us/library/dd991317.aspx

Enum.TryParse is new in .NET 4. If you're stuck on a previous version, you'll have to use the non-typesafe Enum.Parse method (which throws an exception in case of conversion failure, instead of returning false), like so:

try
{
    Types t = (Types)Enum.Parse(typeof(Types), yourString);
    // use t
}
catch(ArgumentException)
{
    // yourString does not contain a valid Types value
}

Enum.Parse also has an overload for case insensitiveness.

回答2:

So, you want: Enum.Parse(typeof(Types), postbackValue)

or did I miss something?

回答3:

If I understood correctly, you can do:

Types fooEnum = Enum.Parse(typeof(Types), "foo");

See: http://msdn.microsoft.com/en-us/library/essfb559.aspx