Cast string.Empty to (generic) T in C#?

Question

I have a utility method which returns a strongly typed value from an old .INI configuration type file, with the signature

internal static T GetIniSetting<T>(string config, string key, T defVal = default(T))

I want strings to be special, in that I would like the default value for defaultValue to be string.Empty, not default(string) (i.e. null), in the case when the coder hasn't specified a default value.

if (cantFindValueInIniFile == true) { if ((typeof(T) == typeof(string)) && (defaultValue == null)) { // *** Code needed here - Cannot convert string to <T>*** return (T)string.Empty; } return defaultValue; }

I've tried hard casting, and the as keyword, to no avail.

Invoking the powers of LSP didn't seem very fitting for this particular case... — user166390
– user166390, Commented Jun 8, 2012 at 5:10

leppie · Accepted Answer · 2012-06-08 04:51:49Z

The 'hacky' way:

return (T)(object)string.Empty;

Notes:

Pretty safe as you have check pre-conditions.
Performance penalty unnoticeable on reference types.

smartcaveman · Accepted Answer · 2012-06-08 04:52:21Z

You have to do it like this: (T)(object)(string.Empty).

Also, a minor optimization is to store this in a static readonly string field so that you don't have to do the casts but one time per generic parameter (instead of per method call)

Phillip Ngan · Accepted Answer · 2012-06-08 04:54:24Z

If I'm not mistaken, the last parameter in GetIniSetting is optional, and you will get default(string) only if you don't provide anything for it. So to use string.Empty as a default string value make the call like:

string value = GetIniSetting<string>(config, key, string.Empty);

You are mistaken. A string is a reference type, so you can pass in null

Collectives™ on Stack Overflow

Cast string.Empty to (generic) T in C#?

3 Answers 3

Comments

2 Comments

2 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

2 Comments

2 Comments

Linked

Related