define a List like List int string

Question

I need a two column list like   List lt int string gt  mylist  new List lt int string gt       it says     using the generic type System collection generic List lt T gt  requires 1 type arguments

User · Answer

Since your example uses a generic List  I assume you don t need an index or unique constraint on your data  A List may contain duplicate values  If you want to insure a unique key  consider using a Dictionary lt TKey  TValue gt      var list   new List lt Tuple lt int string gt  gt      list Add Tuple Create 1   Andy     list Add Tuple Create 1   John     list Add Tuple Create 3   Sally      foreach  var item in list        Console WriteLine item Item1 ToString         Console WriteLine item Item2

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With the new ValueTuple from C  7  VS 2017 and above   there is a new solution   List lt  int string  gt  mylist  new List lt  int string  gt       Which creates a list of ValueTuple type  If you re targeting  Net Framework 4 7  or  Net Core  it s native  otherwise you have to get the ValueTuple package from nuget   It s a struct opposing to Tuple  which is a class  It also has the advantage over the Tuple class that you could create a named tuple  like this   var mylist   new List lt  int myInt  string myString  gt       That way you can access like mylist 0  myInt and mylist 0  myString

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List lt Tuple lt string  DateTime  string gt  gt  mylist   new List lt Tuple lt string  DateTime string gt  gt     mylist Add new Tuple lt string  DateTime  string gt  Datei Info Dateiname  Datei Info Datum  Datei Info Gr    e    for  int i   0  i  lt  mylist Count  i           Console WriteLine mylist i

User · Answer

For that  you could use a Dictionary where the int is the key    new Dictionary lt int  string gt       If you really want to use a list  it could be a List lt Tuple lt int string gt  gt    but  Tuple class is readonly  so you have to recreate the instance to modifie it

User · Answer

Not sure about your specific scenario  but you have three options   1   use Dictionary lt        2   create a wrapper class around your values and then you can use List 3   use Tuple

User · Answer

You could use an immutable struct  public struct Data       public Data int intValue  string strValue                IntegerData   intValue          StringData   strValue             public int IntegerData   get  private set        public string StringData   get  private set       var list   new List lt Data gt       Or a KeyValuePair lt int  string gt   using Data   System Collections Generic KeyValuePair lt int  string gt      var list   new List lt Data gt     list Add new Data 12345   56789

User · Answer

Use C  Dictionary datastructure it good for you     Dictionary lt string  int gt  dict   new Dictionary lt string  int gt     dict Add  one   1   dict Add  two   2     You can retrieve data from Ditionary in a simple way    foreach  KeyValuePair lt string  int gt  pair in dict        MessageBox Show pair Key ToString        -       pair Value ToString           For more example using C  Dictionary     C  Dictionary  Navi

User · Answer

Depending on your needs  you have a few options here   If you don t need to do key value lookups and want to stick with a List lt  gt   you can make use of Tuple lt int  string gt    List lt Tuple lt int  string gt  gt  mylist   new List lt Tuple lt int  string gt  gt         add an item mylist Add new Tuple lt int  string gt  someInt  someString      If you do want key value lookups  you could move towards a Dictionary lt int  string gt    Dictionary lt int  string gt  mydict   new Dictionary lt int  string gt         add an item mydict Add someInt  someString

[c#] define a List like List<int,string>?

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