All possible array initialization syntaxes

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What are all the array initialization syntaxes that are possible with C

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Enumerable Repeat String Empty  count  ToArray     Will create array of empty strings repeated  count  times  In case you want to initialize array with same yet special default element value  Careful with reference types  all elements will refer same object

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These are the current declaration and initialization methods for a simple array   string   array   new string 2      creates array of length 2  default values string   array   new string      A    B        creates populated array of length 2 string   array      A     B        creates populated array of length 2 string   array   new      A    B        created populated array of length 2   Note that other techniques of obtaining arrays exist  such as the Linq ToArray   extensions on IEnumerable lt T gt    Also note that in the declarations above  the first two could replace the string   on the left with var  C  3    as the information on the right is enough to infer the proper type  The third line must be written as displayed  as array initialization syntax alone is not enough to satisfy the compiler s demands  The fourth could also use inference  So if you re into the whole brevity thing  the above could be written as  var array   new string 2      creates array of length 2  default values var array   new string      A    B        creates populated array of length 2 string   array      A     B        creates populated array of length 2 var array   new      A    B        created populated array of length 2

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For Class initialization  var page1   new Class1    var page2   new Class2    var pages   new UIViewController     page1  page2

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For the class below   public class Page        private string data       public Page                    public Page string data                this Data   data             public string Data               get                       return this data                    set                       this data   value                      you can initialize the array of above object as below   Pages   new Page     new Page  a string        Hope this helps

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var contacts   new         new                Name     Eugene Zabokritski           PhoneNumbers   new      206-555-0108    425-555-0001               new                Name     Hanying Feng           PhoneNumbers   new      650-555-0199

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You can also create dynamic arrays i e  you can first ask the size of the array from the user before creating it   Console Write  Enter size of array    int n   Convert ToInt16 Console ReadLine      int   dynamicSizedArray  new int n      Here we have created an array of size n Console WriteLine  Input Elements    for int i 0 i lt n i           dynamicSizedArray i    Convert ToInt32 Console ReadLine        Console WriteLine  Elements of array are      foreach  int i in dynamicSizedArray        Console WriteLine i     Console ReadKey

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In case you want to initialize a fixed array of pre-initialized equal  non-null or other than default  elements  use this   var array   Enumerable Repeat string Empty  37  ToArray      Also please take part in this discussion

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The array creation syntaxes in C  that are expressions are   new int 3  new int 3    10  20  30   new int     10  20  30   new     10  20  30     In the first one  the size may be any non-negative integral value and the array elements are initialized to the default values   In the second one  the size must be a constant and the number of elements given must match  There must be an implicit conversion from the given elements to the given array element type   In the third one  the elements must be implicitly convertible to the element type  and the size is determined from the number of elements given   In the fourth one the type of the array element is inferred by computing the best type  if there is one  of all the given elements that have types  All the elements must be implicitly convertible to that type  The size is determined from the number of elements given  This syntax was introduced in C  3 0   There is also a syntax which may only be used in a declaration   int   x     10  20  30      The elements must be implicitly convertible to the element type  The size is determined from the number of elements given      there isn t an all-in-one guide   I refer you to C  4 0 specification  section 7 6 10 4  Array Creation Expressions

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Trivial solution with expressions  Note that with NewArrayInit you can create just one-dimensional array    NewArrayExpression expr   Expression NewArrayInit typeof int   new     Expression Constant 2   Expression Constant 3      int   array   Expression Lambda lt Func lt int   gt  gt  expr  Compile         compile and call callback

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Just a note The following arrays  string   array   new string 2   string   array2   new string      quot A quot    quot B quot     string   array3      quot A quot     quot B quot     string   array4   new      quot A quot    quot B quot      Will be compiled to  string   array   new string 2   string   array2   new string      quot A quot    quot B quot     string   array3   new string      quot A quot    quot B quot     string   array4   new string      quot A quot    quot B quot

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Example to create an array of a custom class Below is the class definition  public class DummyUser       public string email   get  set        public string language   get  set       This is how you can initialize the array  private DummyUser   arrDummyUser   new DummyUser         new DummyUser         email    quot abc xyz email com quot          language    quot English quot             new DummyUser         email    quot def email com quot          language    quot Spanish quot

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Repeat without LINQ   float   floats   System Array ConvertAll new float 16   v   gt  1 0f

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int   array   new int 4    array 0    10  array 1    20  array 2    30    or  string   week   new string     Sunday   Monday   Tuesday      or  string   array      Sunday     Monday       and in multi dimensional array      Dim i  j As Integer     Dim strArr 1  2  As String      strArr 0  0     First  0 0       strArr 0  1     Second  0 1        strArr 1  0     Third  1 0       strArr 1  1     Fourth  1 1

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Another way of creating and initializing an array of objects   This is similar to the example which  Amol has posted above  except this one uses constructors   A dash of polymorphism sprinkled in  I couldn t resist   IUser   userArray   new IUser         new DummyUser  abc cde edu    Gibberish        new SmartyUser  pga lna it    Italian    Engineer        Classes for context   interface IUser       string EMail   get             immutable  so get only an no set     string Language   get       public class DummyUser   IUser       public DummyUser string email  string language                m email   email          m language   language             private string m email      public string EMail               get   return m email               private string m language      public string Language               get   return m language             public class SmartyUser   IUser       public SmartyUser string email  string language  string occupation                m email   email          m language   language          m occupation   occupation             private string m email      public string EMail               get   return m email               private string m language      public string Language               get   return m language               private string m occupation

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hi just to add another way  from this page   https   docs microsoft com it-it dotnet api system linq enumerable range view netcore-3 1 you can use this form If you want to Generates a sequence of integral numbers within a specified range strat 0 to 9  using System Linq       public int   arrayName   Enumerable Range 0  9  ToArray

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These are the current declaration and initialization methods for a simple array      string   array   new string 3       string   array2   new string      quot 1 quot    quot 2 quot    quot 3 quot         string   array3      quot 1 quot    quot 2 quot    quot 3 quot         string   array4   new      quot 1 quot    quot 2 quot    quot 3 quot

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Non-empty arrays   var data0   new int 3  var data1   new int 3    1  2  3   var data2   new int     1  2  3   var data3   new     1  2  3    var data4     1  2  3   is not compilable  Use int   data5     1  2  3   instead    Empty arrays   var data6   new int 0  var data7   new int       var data8   new         and int   data9   new        are not compilable  var data10       is not compilable  Use int   data11        instead             As an argument of a method  Only expressions that can be assigned with the var keyword can be passed as arguments    Foo new int 2   Foo new int 2    1  2    Foo new int     1  2    Foo new     1  2    Foo   1  2    is not compilable  Foo new int 0   Foo new int        Foo     is not compilable

[c#] All possible array initialization syntaxes

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