Declaration Error of Dictionary with Interface

Question

0.00/5 (No votes)

See more:

Hi,

I tried to declare a dictionary have a string as the key and an object a the value. I declared it with the help of the interfaces. This is my code

C#

ICollection<KeyValuePair<string, ICollection<DemoProperty>>> Test = new Dictionary<string, List<DemoProperty>>();

Its getting the coversion Error.

But there is no Error when I declare as below

C#

ICollection<KeyValuePair<string, ICollection<DemoProperty>>> Test = new List<KeyValuePair<string, ICollection<DemoProperty>>>();

and I know this can declare as below also

C#

Dictionary<string, ICollection<DemoProperty>> Test = new Dictionary<string, ICollection<DemoProperty>>

What is the exact error on the first statement and how can I proceed with the first statatement. Hope you all understand my questions.

Posted 1-Jun-15 0:35am

Libin C Jacob

Updated 1-Jun-15 0:39am

v2

Add a Solution

Comments

BillWoodruff 1-Jun-15 15:31pm

Why are you using ICollection ?

What did you expect in the first example: you are using signatures that don't match.

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Andy Lanng · Answer 1 · 2015-06-01T00:48:00

You cannot recast the value type at declaration of the dictionary:

C#

ICollection<keyvaluepair><string,>>> Test = new Dictionary<string,>>();

Test.Add(new KeyValuePair<string,>>("a",new List<demoproperty>()));

</demoproperty></keyvaluepair>

If you could then you would not be able to add any ICollection, only List<demoproperty> which is not what your declaration states

You can instantiate an ICollection<x> as a Dictionary<x> because Dictionary<tkey,tvalue>; inherits ICollection<tkey,tvalue> but if you change the generic types then they won't match.

Tomas Takac · Answer 2 · 2015-06-01T00:47:00

Solution 1

In your first declaration you use List instead of ICollection. This works:

C#

ICollection<KeyValuePair<string, ICollection<DemoProperty>>> Test = new Dictionary<string, ICollection<DemoProperty>>();

Posted 1-Jun-15 0:47am

Tomas Takac