How to add item to the beginning of List T

Question

I want to add a  Select One  option to a drop down list bound to a List lt T gt     Once I query for the List lt T gt   how do I add my initial Item  not part of the data source  as the FIRST element in that List lt T gt     I have      populate ti from data                List lt MyTypeItem gt  ti   MyTypeItem GetTypeItems          create initial entry     MyTypeItem initialItem   new MyTypeItem        initialItem TypeItem    Select One       initialItem TypeItemID   0  ti Add initialItem    lt  -- want this at the TOP         then      DropDownList1 DataSource   ti

User · Answer

Since  NET 4 7 1  you can use the side-effect free Prepend   and Append    The output is going to be an IEnumerable      Creating an array of numbers var ti   new List lt int gt    1  2  3        Prepend and Append any value of the same type var results   ti Prepend 0  Append 4       output is 0  1  2  3  4 Console WriteLine string Join       results

User · Answer

Update  a better idea  set the  AppendDataBoundItems  property to true  then declare the  Choose item  declaratively  The databinding operation will add to the statically declared item    lt asp DropDownList ID  ddl  runat  server  AppendDataBoundItems  true  gt       lt asp ListItem Value  0  Text  Please choose     gt  lt  asp ListItem gt   lt  asp DropDownList gt    http   msdn microsoft com en-us library system web ui webcontrols listcontrol appenddatabounditems aspx  -Oisin

User · Answer

Update  a better idea  set the  AppendDataBoundItems  property to true  then declare the  Choose item  declaratively  The databinding operation will add to the statically declared item    lt asp DropDownList ID  ddl  runat  server  AppendDataBoundItems  true  gt       lt asp ListItem Value  0  Text  Please choose     gt  lt  asp ListItem gt   lt  asp DropDownList gt    http   msdn microsoft com en-us library system web ui webcontrols listcontrol appenddatabounditems aspx  -Oisin

User · Answer

Update  a better idea  set the  AppendDataBoundItems  property to true  then declare the  Choose item  declaratively  The databinding operation will add to the statically declared item    lt asp DropDownList ID  ddl  runat  server  AppendDataBoundItems  true  gt       lt asp ListItem Value  0  Text  Please choose     gt  lt  asp ListItem gt   lt  asp DropDownList gt    http   msdn microsoft com en-us library system web ui webcontrols listcontrol appenddatabounditems aspx  -Oisin

User · Answer

Use the Insert method   ti Insert 0  initialItem

User · Answer

Use List lt T gt  Insert  While not relevant to your specific example  if performance is important also consider using LinkedList lt T gt  because inserting an item to the start of a List lt T gt  requires all items to be moved over  See When should I use a List vs a LinkedList

User · Answer

Use Insert method of List lt T gt       List Insert Method  Int32  T   Inserts an element into the List at the specified index    var names   new List lt string gt     John    Anna    Monica     names Insert 0   Micheal       Insert to the first element

User · Answer

Use the Insert method   ti Insert 0  initialItem

User · Answer

Update  a better idea  set the  AppendDataBoundItems  property to true  then declare the  Choose item  declaratively  The databinding operation will add to the statically declared item    lt asp DropDownList ID  ddl  runat  server  AppendDataBoundItems  true  gt       lt asp ListItem Value  0  Text  Please choose     gt  lt  asp ListItem gt   lt  asp DropDownList gt    http   msdn microsoft com en-us library system web ui webcontrols listcontrol appenddatabounditems aspx  -Oisin

User · Answer

Since  NET 4 7 1  you can use the side-effect free Prepend   and Append    The output is going to be an IEnumerable      Creating an array of numbers var ti   new List lt int gt    1  2  3        Prepend and Append any value of the same type var results   ti Prepend 0  Append 4       output is 0  1  2  3  4 Console WriteLine string Join       results

User · Answer

Use the Insert method   ti Insert 0  initialItem

User · Answer

Use List lt T gt  Insert  While not relevant to your specific example  if performance is important also consider using LinkedList lt T gt  because inserting an item to the start of a List lt T gt  requires all items to be moved over  See When should I use a List vs a LinkedList

User · Answer

Use the Insert method   ti Insert 0  initialItem

User · Answer

Use Insert method of List lt T gt       List Insert Method  Int32  T   Inserts an element into the List at the specified index    var names   new List lt string gt     John    Anna    Monica     names Insert 0   Micheal       Insert to the first element

[c#] How to add item to the beginning of List<T>?

Examples related to c#

Examples related to drop-down-menu

Examples related to generic-list