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1. Top results related to how to initialize a dictionary in c# with example

   • Initialize a Dictionary with values in C# 2.0

     Top Answer

     Answered Jul 19, 2013 · 10 votes

     But it doesn't work in C# 2.0. Is there any workaround for this without using Add or basing on an already existing collection?

     No. The closest I can think of would be to write your own DictionaryBuilder type to make it simpler:

     public class DictionaryBuilder<TKey, TValue>{ private Dictionary<TKey, TValue> dictionary = new Dictionary<TKey, TValue> dictionary(); public DictionaryBuilder<TKey, TValue> Add(TKey key, TValue value) { if (dictionary == null) { throw new InvalidOperationException("Can't add after building"); } dictionary.Add(key, value); return this; } public Dictionary<TKey, TValue> Build() { Dictionary<TKey, TValue> ret = dictionary; dictionary = null; return ret; }}

     Then you can use:

     Dictionary<string, int> x = new DictionaryBuilder<string, int>() .Add("Foo", 10) .Add("Bar", 20) .Build();

     This is at least a single expression still, which is useful for fields where you want to initialize at the point of declaration.

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   • In C#: How to declare a generic Dictionary with a type as key and an IEnumerable<> of that type as value?

     Top Answer

     Answered Dec 01, 2017 · 21 votes

     You may not even need a dictionary to be able to do this - but that depends on your needs. If you only ever need 1 such list per type per appdomain (i.e. the "dictionary" is static), the following pattern can be efficient and promotes type-inference nicely:

     interface IBase {}-static class Container { static class PerType<T> where T : IBase { public static IEnumerable<T> list; } public static IEnumerable<T> Get<T>() where T : IBase => PerType<T>.list; public static void Set<T>(IEnumerable<T> newlist) where T : IBase => PerType<T>.list = newlist; public static IEnumerable<T> GetByExample<T>(T ignoredExample) where T : IBase => Get<T>(); }

     Note that you should think carefully before adopting this approach about the distinction between compile-time type and run-time type. This method will happily let you store a runtime-typed IEnumerable<SomeType> variable both under SomeType and -if you cast it- under any of SomeType's base types, including IBase, with neither a runtime nor compiletype error - which might be a feature, or a bug waiting to happen, so you may want an if to check that.

     Additionally, this approach ignores threading; so if you want to access this data-structure from multiple threads, you probably want to add some locking. Reference read/writes are atomic, so you're not going to get corruption if you fail to lock, but stale data and race conditions are certainly possible.

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     2/5

   • How to initialize a double array with various values using switch case in C#

     Top Answer

     Answered Jul 15, 2015 · 0 votes

     You were close, you just have to use new to initialize the arrays:

     double [] test1; int value; // Which I will get it from DBSwitch (value){case 1: test1 = new double[] {1, 0, 0,1}; break;case 2: test1 = new double[] {0, 0, 0,1}; break;case 3: test1 = new double[] {0, 0, 1,1}; break;case 4: test1 = new double[] {1, 0, 1,1}; break;}

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     3/5

   • How to Draw a rectangle on image using Emgu CV libraries in C#. with an example

     Top Answer

     Answered Nov 25, 2021 · 1 votes

     Most things you know how to do in Python with OpenCV can be done in C# Emgu with CvInvoke.

     For instance, this site shows the Rectangle method for drawing a rectangle onto a given image.

     public static void Rectangle( IInputOutputArray img, Rectangle rect, MCvScalar color, int thickness = 1, LineType lineType = LineType.EightConnected, int shift = 0)

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     4/5

   • How to initialize an array with numbers separated by a specific interval in C#

     Top Answer

     Answered Feb 22, 2012 · 18 votes

     An interesting fact is that every answer posted so far has fixed the bug in your proposed code, but only one has called out that they've done so.

     Binary floating point numbers have representation error when dealing with any quantity that is not a fraction of an exact power of two. ("3.0/4.0" is a representable fraction because the bottom is a power of two; "1.0/10.0" is not.)

     Therefore, when you say:

     for(i = 0; i < 10; i++) { myArray[i] = increment; increment += 0.1; }

     You are not actually incrementing "increment" by 1.0/10.0. You are incrementing it by the closest representable fraction that has an exact power of two on the bottom. So in fact this is equivalent to:

     for(i = 0; i < 10; i++) { myArray[i] = increment; increment += (exactly_one_tenth + small_representation_error);}

     So, what is the value of the tenth increment? Clearly it is 10 * (exactly_one_tenth + small_representation_error) which is obviously equal to exactly_one + 10 * small_representation_error. You have multiplied the size of the representation error by ten.

     Any time you repeatedly add together two floating point numbers, each subsequent addition increases the total representation error of the sum slightly and that adds up, literally, to a potentially large error. In some cases where you are summing thousands or millions of small numbers the error can become far larger than the actual total.

     The far better solution is to do what everyone else has done. Recompute the fraction from integers every time. That way each result gets its own small representation error; it does not accumulate the representation errors of previously computed results.

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2. learn.microsoft.com › en-us › dotnetHow to initialize a dictionary with a collection initializer - C#

   learn.microsoft.com › en-us › dotnet

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   Learn how to initialize a dictionary in C#, using either the Add method or an index initializer. This example shows both options.

3. stackoverflow.com › questions › 17047602Proper way to initialize a C# dictionary with values

   stackoverflow.com › questions › 17047602

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   With C# 6.0, you can create a dictionary in the following way: var dict = new Dictionary<string, int> { ["one"] = 1, ["two"] = 2, ["three"] = 3 }; It even works with custom types.

4. People also ask

   How to initialize a dictionary with values?

   • You can declare a dictionary and initialize it with values by using the collection initializer syntax. Within the initializer block, you have two options for adding key/value pairs to the dictionary: Indexer syntax, like [key] = value. Curly brace syntax, like { key, value }. I’ll show examples of both options below.

   C# - Initialize a dictionary | MAKOLYTE

   makolyte.com/csharp-initialize-a-dictionary/

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   How to initialize a dictionary in C#?

   • In the second initialization, the left side of the assignment is the key and the right side is the value, using an object initializer for StudentName. Learn how to initialize a dictionary in C#, using either the Add method or an index initializer. This example shows both options.

   How to initialize a dictionary with a collection initializer - C#

   learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/how-to-initialize-a-dictionary-with-a-collection-initializer

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   How do I create a dictionary in C#?

   • With C# 6.0, you can create a dictionary in the following way: ["one"] = 1, ["two"] = 2, ["three"] = 3 It even works with custom types. That's a new syntax I wasn't familiar with. Thanks. I didn't know this syntax, thanks. It makes it easy to copy and paste dictionaries of data from other languages such as Lua.

   Proper way to initialize a C# dictionary with values

   stackoverflow.com/questions/17047602/proper-way-to-initialize-a-c-sharp-dictionary-with-values

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   Why is it called a dictionary in C#?

   • It's called a Dictionary because the key is used to look up the corresponding value, just like in a real dictionary. The good thing is that the dictionary is a generic, so we can use it to store values of any type. To initialize a dictionary in C#, we first need to provide the type for the key and the type for the value.

   C# Dictionary: Complete Guide [2023] - Josip Miskovic

   josipmisko.com/posts/c-sharp-dictionary

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5. stackoverflow.com › questions › 10998961c# - Adding values to a dictionary via inline initialization ...

   stackoverflow.com › questions › 10998961

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   Mar 10, 2017 · Before C# 6, you could initialize dictionaries and other associative containers using the following syntax. Notice that instead of indexer syntax, with parentheses and an assignment, it uses an object with multiple values: var moreNumbers = new Dictionary<int, string>. {.

6. www.techiedelight.com › initialize-dictionary-csharpInitialize a Dictionary in C# | Techie Delight

   www.techiedelight.com › initialize-dictionary-csharp

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   Apr 6, 2024 · This post will discuss how to initialize a dictionary in C#... To initialize a dictionary, we can enclose each set of key-value in curly braces. Internally for each pair, the compiler makes a call to Dictionary's `Add()` method.

7. www.gyata.ai › c-sharp › c-initialize-dictionaryGuide to Initialize a Dictionary in C# | C# Tutorial

   www.gyata.ai › c-sharp › c-initialize-dictionary

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   Dec 8, 2023 · In this tutorial, we will delve into how to initialize a dictionary in C#, accompanied by illustrative examples. Familiarity with dictionaries can be a real game-changer in your coding journey, so let's get started! 1. Initializing an Empty Dictionary; The simplest way to initialize a dictionary in C# is to create an empty dictionary.

8. makolyte.com › csharp-initialize-a-dictionaryC# - Initialize a dictionary | makolyte

   makolyte.com › csharp-initialize-a-dictionary

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   Sep 12, 2023 · You can declare a dictionary and initialize it with values by using the collection initializer syntax. Within the initializer block, you have two options for adding key/value pairs to the dictionary: Indexer syntax, like [key] = value. Curly brace syntax, like { key, value }. I’ll show examples of both options below.

9. josipmisko.com › posts › c-sharp-dictionaryC# Dictionary: Complete Guide [2023] – Josip Miskovic

   josipmisko.com › posts › c-sharp-dictionary

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   Jan 26, 2023 · To initialize a dictionary in C#, we first need to provide the type for the key and the type for the value. For example, for a dictionary that stores the name and age of a person, the initialization would be: C# Dictionary<string, int> nameToAge = new Dictionary<string, int>(); The first type inside the angle brackets is the key type.