TryGet

Simple, fluent dictionary value retrieval.

As anyone familiar wth C# knows, you cannot use the as or is keyword to change or check types with the out var syntax.

For example, something like this is not possible:

var dictionary = new Dictionary<string, object>();

if (dictionary.TryGetValue("key", out as string val)) { }

This project aims to address the above desired use case.

Install

Package manager console:
install-package tryget

Dotnet CLI:
dotnet add package tryget

Quick Start

using TryGet;

// Check if the key exists
if (dictionary.TryGet("key")) { }

// Check if the key exists and can be cast to string
if (dictionary.TryGet("key").As<string>()) { }

// Capture the value at key "key" if it exists and can be cast to string, otherwise default
var val = dictionary.TryGet("key").As<string>().OrDefault();

// Same as above, but with custom default value
var val = dictionary.TryGet("key").As<string>().OrDefault("Not a string.");

// Check if the key exists and capture the value with 'out' keyword
if (dictionary.TryGet("key").As<string>(out var val)) { }

More Examples

Let's set up our dictionary.

TryGet works on any IDictionary<TKey, TValue>, but it's most useful on <string, object> dictionaries commonly used to pass custom data.

We will assume this dictionary exists for our examples.

var dictionary = new Dictionary<string, object>
{
    { "key", new { } },
    { "string", "This is a string." },
    { "number", 15 }
};

Check if a value

...exists

if (dictionary.TryGet("key"))
{
  // "key" exists, do stuff
}

...exists and is of a certain type

if (dictionary.TryGet("string").As<string>())
{
  // "string" exists and is a string
}

You can also check casts to polymorphic types.

class Animal { }
class Cat : Animal, IHasNineLives { }
class Dog : Animal { }
interface IHasNineLives { }
...
var animals = new Dictionary<string, Animal>
{
    { "cat", new Cat() },
    { "dog", new Dog() }
}

if (animals.TryGet("cat").As<Cat>())
{
    // Success
}
if (animals.TryGet("cat").As<Dog>()}
{
    // Not success
}

Interfaces work too

if (animals.TryGet("cat").As<IHasNineLives>())
{
    // Success
}
if (animals.TryGet("dog").As<IHasNineLives>())
{
    // Not success
}

I guess this works too if you're just a mad lad

if (animals.TryGet("cat").As<object>().As<Animal>().As<Cat>())
{
    // Success
}

Get a value

...if it exists

var val = dictionary.TryGet("number");

// val = 15 (boxed to an object)

...if it exists and is of a certain type, otherwise return the default

var val = dictionary.TryGet("number").As<int>().OrDefault();

// val = 15

var val = dictionary.TryGet("number").As<string>().OrDefault();

// val = null

OrDefault() also supports custom default values

var val = dictionary.TryGet("number").As<string>().OrDefault("Not a string.");

// val = "Not a string."

You can also perform a check and capture the value with out

if (dictionary.TryGet("number").As(out var val))
{
    // val = 15 (boxed to an object)
}

The real value-add here is being able to cast with out

if (dictionary.TryGet("number").As<int>(out var val)){
    // val = 15
}

Using the TryGet result

Calling .TryGet() returns a result of type TryGetResult<TValue>, which can be used directly instead of the fluent methods.

var result = dictionary.TryGet("number");
if (result.IsSuccess)
{
    // Success!
    // Do something with result.Value
}

The result also supports being cast directly to a compatible result type.

string stringValue = (string)result;

The only type you cannot cast to is bool; this is a special case used for indicating success.

Value will throw a NoValueException if the key did not exist:

var result = dictionary.TryGet("does_not_exist");
var val = result.Value;  // !!!

It will also throw a NoValueException if the retrieved value was not the correct type:

var result = dictionary.TryGet("string").As<int>();
var val = result.Value; // !!!