Best way to check if a drop down list contains a value

Question

When the user navigates to a new page  this ddl s selected index is determined by a cookie  but if the ddl doesn t contain that cookie s value  then I d like it to be set the 0  What method would I use for the ddl  Is a loop the best way  or is there a simply if statement I can perform   This is what I ve attempted  but it doesn t return a bool   if    ddlCustomerNumber Items FindByText  GetCustomerNumberCookie   ToString           ddlCustomerNumber SelectedIndex   0

User · Answer

you can use the   operator instead of if  ddlCustomerNumber SelectedValue   ddlType Items FindByValue GetCustomerNumberCookie   ToString       null   GetCustomerNumberCookie   ToString      0

User · Answer

If the function return Nothing  you can try this below  if  ddlCustomerNumber Items FindByText      GetCustomerNumberCookie   ToString       Nothing

User · Answer

If 0 is your default value  you can just use a simple assignment   ddlCustomerNumber SelectedValue   GetCustomerNumberCookie   ToString      This automatically selects the proper list item  if the DDL contains the value of the cookie  If it doesn t contain it  this call won t change the selection  so it stays at the default selection  If the latter one is the same as value 0  then it s the perfect solution for you   I use this mechanism quite a lot and find it very handy

User · Answer

There are two methods that come to mind   You could use Contains like so   if  ddlCustomerNumber Items Contains new      ListItem GetCustomerNumberCookie   ToString                   code here     or modifying your current strategy   if  ddlCustomerNumber Items FindByText      GetCustomerNumberCookie   ToString       null               code here     EDIT   There s also a DropDownList Items FindByValue that works the same way as FindByText  except it searches based on values instead

User · Answer

That will return an item  Simply change to   if  ddlCustomerNumber Items FindByText  GetCustomerNumberCookie   ToString       null      ddlCustomerNumber SelectedIndex   0

User · Answer

ListItem item   ddlComputedliat1 Items FindByText  Amt D    if  item    null        ddlComputedliat1 Items Insert 1  lblnewamountamt Text

User · Answer

What about this   ListItem match   ddlCustomerNumber Items FindByText      GetCustomerNumberCookie   ToString     if  match    null      ddlCustomerNumber SelectedIndex   0    else       match Selected   true     you ll probably select that cookie value

User · Answer

On C  this works           if  DDLAlmacen Items Count  gt  0                        if  DDLAlmacen Items FindByValue  AlmacenDefectoAndes   Value     AlmacenDefectoAndes                                 DDLAlmacen SelectedValue    AlmacenDefectoAndes                             Update   Translating the code above to Visual Basic doesn t work  It throws  System NullReferenceException  Object reference not set to an instance of an object     So  for this to work on Visual Basic  I had to change the code like this           If DDLAlmacen Items Count  gt  0 Then             If DDLAlmacen Items Contains New ListItem  AlmacenDefectoAndes    Then                 DDLAlmacen SelectedValue    AlmacenDefectoAndes              End If         End If

User · Answer

Sometimes the value needs to be trimmed of whitespace or it won t be matched  in such case this additional step can be used  source    if   DropDownList  myControl1  Items Cast lt ListItem gt    Select i   gt  i Value Trim      ctrl value Trim    FirstOrDefault      null

User · Answer

You could try checking to see if this method returns a null     if  ddlCustomerNumber Items FindByText GetCustomerNumberCookie   ToString       null      ddlCustomerNumber SelectedIndex   0

[c#] Best way to check if a drop down list contains a value?

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