How can I find a specific element in a List T

Question

My application uses a list like this   List lt MyClass gt  list   new List lt MyClass gt      Using the Add method  another instance of MyClass is added to the list   MyClass provides  among others  the following methods   public void SetId String Id   public String GetId      How can I find a specific instance of MyClass by means of using the GetId method  I know there is the Find method  but I don t know if this would work here

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Or if you do not prefer to use LINQ you can do it the old-school way   List lt MyClass gt  list   new List lt MyClass gt     foreach  MyClass element in list        if  element GetId       heres where you put what you are looking for                  break     If you only want to find the first instance a break here would be best for your application

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var list   new List lt MyClass gt     var item   list Find  x   gt  x GetId       TARGET ID       or if there is only one and you want to enforce that something like SingleOrDefault may be what you want  var item   list SingleOrDefault  x   gt  x GetId       TARGET      if   item    null       throw new Exception

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public List lt DealsCategory gt  DealCategory   get  set    int categoryid   Convert ToInt16 dealsModel DealCategory Select x   gt  x Id

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Use a lambda expression  MyClass result   list Find x   gt  x GetId       xy        Note  C  has a built-in syntax for properties  Instead of writing getter and setter methods  as you might be used to from Java   write  private string  id  public string Id       get               return  id            set                id   value            value is a contextual keyword known only in the set accessor  It represents the value assigned to the property   Since this pattern is often used  C  provides  auto-implemented properties  They are a short version of the code above  however  the backing variable is hidden and not accessible  it is accessible from within the class in VB  however    public string Id   get  set      You can simply use properties as if you were accessing a field   var obj   new MyClass    obj Id    xy            Calls the setter with  xy  assigned to the value parameter  string id   obj Id      Calls the getter      Using properties  you would search for items in the list like this  MyClass result   list Find x   gt  x Id     xy         You can also use auto-implemented properties if you need a read-only property   public string Id   get  private set      This enables you to set the Id within the class but not from outside  If you need to set it in derived classes as well you can also protect the setter  public string Id   get  protected set        And finally  you can declare properties as virtual and override them in deriving classes  allowing you to provide different implementations for getters and setters  just as for ordinary virtual methods     Since C  6 0  Visual Studio 2015  Roslyn  you can write getter-only auto-properties with an inline initializer  public string Id   get       A07      Evaluated once when object is initialized    You can also initialize getter-only properties within the constructor instead  Getter-only auto-properties are true read-only properties  unlike auto-implemented properties with a private setter   This works also with read-write auto-properties   public string Id   get  set       A07     Beginning with C  6 0 you can also write properties as expression-bodied members  public DateTime Yesterday   gt  DateTime Date AddDays -1      Evaluated at each call     Instead of public DateTime Yesterday   get   return DateTime Date AddDays -1         See   NET Compiler Platform   Roslyn    nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp New Language Features in C  6  Starting with C  7 0  both  getter and setter  can be written with expression bodies   public string Name       get   gt   name                                    getter     set   gt   name   value                            setter     Note that in this case the setter must be an expression  It cannot be a statement  The example above works  because in C  an assignment can be used as an expression or as a statement  The value of an assignment expression is the assigned value where the assignment itself is a side effect  This allows you to assign a value to more than one variable at once  x   y   z   0 is equivalent to x    y    z   0   and has the same effect as the statements x   0  y   0  z   0    The next version of the language  C  9 0  probably available in November 2020  will allow read-only  or better initialize-once  properties that you can initialize in an object initializer  This is currently not possible with getter-only properties   public string Name   get  init     var c   new C   Name    c-sharp

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You can create a search variable to hold your searching criteria  Here is an example using database    var query   from o in this mJDBDataset Products               where o ProductStatus    textBox1 Text    o Karrot    textBox1 Text                  o ProductDetails    textBox1 Text    o DepositDate    textBox1 Text                  o SellDate    textBox1 Text              select o    dataGridView1 DataSource   query ToList        Search and Calculate  search   textBox1 Text   cnn Open     string query1   string Format  select   from Products where ProductStatus                     search         SqlDataAdapter da   new SqlDataAdapter query1  cnn    DataSet ds   new DataSet     da Fill ds   Products     SqlDataReader reader   reader   new SqlCommand query1  cnn  ExecuteReader      List lt double gt  DuePayment   new List lt double gt       if  reader HasRows        while  reader Read            foreach  DataRow row in ds Tables  Products   Rows             DuePaymentstring Add row  DuePayment   ToString          DuePayment   DuePaymentstring Select x   gt  double Parse x   ToList                 tdp   0    tdp   DuePayment Sum                              DuePaymentstring Remove Convert ToString DuePaymentstring Count      DuePayment Clear        cnn Close     label3 Text   Convert ToString tdp     Due Payment Count        DuePayment Count     Due Payment string Count      DuePaymentstring Count    tdp   0     DuePaymentstring RemoveRange 0 DuePaymentstring Count      DuePayment RemoveRange 0  DuePayment Count      Search and Calculate   Here  var query  is generating the search criteria you are giving through the search variable  Then  DuePaymentstring Select  is selecting the data matching your given criteria  Feel free to ask if you have problem understanding

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Try    list Find item   gt  item id  myid

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You can also use LINQ extensions   string id    hello   MyClass result   list Where m   gt  m GetId      id  First

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You can solve your problem most concisely with a predicate written using anonymous method syntax   MyClass found   list Find item   gt  item GetID      ID

[c#] How can I find a specific element in a List<T>?

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