VFP里的组合框为什么输入数据不能保存到表,该怎么解决

VFP里的组合框为什么输入数据不能保存到表
有一个组合框 combo1的int属性的代码如下
thisform.combo1.rowsourcetype=0
thisform.combo1.additem (" ")
thisform.combo1.additem ("魏")
thisform.combo1.additem ("李")


combo1的keypress代码如下
LPARAMETERS nKeyCode, nShiftAltCtrl
if nKeyCode=13
 if !empty(this.displayvalue)
  this.additem(this.displayvalue)
 endif
endif


Rowsource Type 6字段

手工输入到COMBO1的数据无法保存，选择的倒可以，请问怎么解决？

[解决办法]
将以下代码粘到 vfp 的 程序(Prg)中运行看一下效果吧:

VB code

Public oform1oform1=Newobject("form1")oform1.ShowReturnDefine Class form1 As Form    DoCreate = .T.    Caption = "Form1"    Name = "Form1"    Add Object combo1 As ComboBox With ;        RowSourceType = 6, ;        RowSource = "t1.name", ;        Height = 24, ;        Left = 252, ;        Top = 36, ;        Width = 100, ;        Name = "Combo1"    Add Object grid1 As Grid With ;        DeleteMark = .F., ;        Height = 200, ;        Left = 24, ;        ReadOnly = .T., ;        Top = 36, ;        Width = 216, ;        Name = "Grid1"    Procedure Load        Create Cursor t1 (Name c(10))        Insert Into t1 Values ('张三')        Insert Into t1 Values ('李四')        Locate    Endproc    Procedure combo1.KeyPress        Lparameters nKeyCode, nShiftAltCtrl        If nKeyCode=13            If Messagebox('确认要将此内容【'+Alltrim(This.DisplayValue)+'】添加到表中吗？',4+32+256,'信息提示')=6                Insert Into t1 Values (Alltrim(This.DisplayValue))            Endif        Endif    EndprocEnddefine