>I have a form with one textbox and i have a toolbar.
>A command button in the toolbar efects a method from the active form.
>The methods code is :
>
>tableupdate(.t.)
>thisform.release
>
>My problem is when i click the command button, the field from the textbox updates blank.
>
>Thanks.

Cemal, the problem here is that when you click on the toolbar button your textbox is not loosing the focus, so it does not validate the entered value.
In general you need the to call custom Form.Writebuffer() method from your button before TABLEUPDATE(), which will take care of that.
Here is tsBaseForm.Writebuffer() from Tasmanian Traders VFP sample.

***********tsBaseForm.Writebuffer()
LOCAL llRetval
llRetVal = .T.

*-- Code to save field value to buffer when
*-- clicking on toolbar without leaving the field
*-- Don't do this for a grid since a grid may change
*-- work areas unexpectedly
IF TYPE("thisform.ActiveControl") == "O" AND ;
    UPPER(thisform.ActiveControl.BaseClass) <> "GRID"
  IF TYPE("thisform.ActiveControl.ControlSource") <> "U" AND ;
      !EMPTY(thisform.ActiveControl.ControlSource)
    IF EVAL(thisform.ActiveControl.ControlSource) <> thisform.ActiveControl.Value
      REPLACE (thisform.ActiveControl.ControlSource) WITH thisform.ActiveControl.Value
      *-- We rely on the fact that we revert the field's value
      *-- in the error event method for the form. 
      llRetVal = (EVAL(thisform.ActiveControl.ControlSource) = thisform.ActiveControl.Value)
    ENDIF
  ENDIF
ENDIF

RETURN llRetVal

All commercial frameworks have similar kinds of Form.WriteBuffer() method in their base form classes.

HTH