How to Add Items to a Multiple-Column Combo Box

• Microsoft Visual FoxPro for Windows, version 3.0

SUMMARY

Combo boxes are designed so that new items can be added to the list or existing items can be selected from the list. You can do the same thing with multiple-column combo boxes. This article shows you how.

MORE INFORMATION

Step-by-Step Procedure

1. Create a new form and place a combo box on it.



2. Add the Orders table from the Testdata database to the data environment.



3. Set the following properties for the combo box:

   
      Property        Value
      -------------------------------------
      Style           0 - Dropdown Combo
      RowSourceType   0 - None
      RowSource       (should be empty)
      ColumnCount     2
      ColumnWidth     50,120
      BoundColumn     1 (this is the default) 

   RowSourceType must be set to 0 and RowSource must be empty when items are added to the combo box programmatically.



4. Place the following code in the Init event of the combo box:

   
      SET EXACT ON   && Comparison done in Valid may be comparing blanks
      SELECT orders
      DO WHILE recno()<10   && Fill the combo box with the first 10 records
   
         ThisForm.Combo1.AddItem(order_id,This.ListCount+1,1)
         ThisForm.Combo1.AddListItem(to_country,This.ListCount,2)
         SKIP
   
      ENDDO
      This.Value=This.List(1)  && Initialize the value of the combo box 

   ListCount is initially 0 because no items are contained in the list. The AddItem method places Order_id in column one. ListCount+1 indicates the first row added. After the AddItem method is called, ListCount is 1. The AddListItem method adds To_country to column two of row one.



5. Place the following code in the Valid event of the combo box to add new entries to the list when the form is running:

   
      in_list=.F.
      IF AT(",",This.DisplayValue)>0
         first=ALLTRIM(LEFT(This.DisplayValue,at(",",This.DisplayValue)-1))
         second=ALLTRIM(RIGHT(This.DisplayValue,LEN(This.DisplayValue);
            -AT(",",This.DisplayValue)))
      ELSE
         first=ALLTRIM(This.DisplayValue)
      ENDIF
   
      FOR I= 1 to This.ListCount
        IF ALLTRIM(first)=ALLTRIM(This.List(I))
          in_list=.T.
          =MESSAGEBOX("Item number is already in list,"+chr(13)+ ;
             "         item not entered","STOP")
        ENDIF
      ENDFOR
   
      IF !in_list
        IF AT(",",This.DisplayValue)=0
          =MESSAGEBOX("Comma followed by description needed,"+chr(13)+ ;
             "        item not entered","STOP")
        ELSE
          This.AddItem(first,This.ListCount+1,1)
          This.AddListItem(second,This.ListCount,2)
          This.Value=""
        ENDIF
      ENDIF 

   In the For loop, This.DisplayValue contains the current entry in the combo box. This.Value has not yet been assigned. If This.DisplayValue is equal to some value already in the combo box list, In_list is set to True and the next section of code is not run. If it is not found in the list, then the entry in the combo box is parsed based on a comma placed between what would be the columns one and two. The parsed items are then added to the list by calling the AddItem and AddListitem methods. This.List(I) contains only the values in column one because the BoundColumn is 1.



6. Run the form. Select items in the list, and add new items to the list by entering the Order_id followed by a comma and the to_country.

Additional query words: listbox VFoxWin

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