Automatically determines whether textbox and cmobobox are empty (traversal Control)

Is it crazy when we have to judge whether each widget is empty on every form? After judging one is the next and the other, let's look at the long string of IF... else! In fact, in the field of object-oriented, we should think of one of the three major features of object-oriented as long as we repeat the same or similar code three or more times: encapsulation.

The commonly used input data controls are textbox and cmobobox. Here I will take them as an example (the tabindex and tag attributes of the control need to be used, the text property does not have the running effect if it replaces the tag property ):

This example is not achieved overnight. It has undergone three major changes:

 

Function Code

First time: the code is relatively long, And the traversal is performed from the control's tabindex attribute to the smallest, the running result is not satisfactory ~

Public shared function isemptytext (byval objs as windows. forms. control. controlcollection) as Boolean 'declares an instance of the control class dim objcon as Control' to start traversing every control in the control class for each objcon in obj' typeof to determine the type if typeof (objcon) is textbox then if objcon. TEXT = "" Then msgbox (objcon. tag. tostring + "cannot be blank", vbokonly + vbexclamation, "warning") objcon. focus () return false exit function end if 'Use typeof to view the control type elseif typeof (objcon) is ComboBox then if objcon. TEXT = "" Then msgbox (objcon. tag. tostring + "cannot be blank", vbokonly + vbexclamation, "warning") objcon. focus () return false exit function end if next return true end Function

Second: integrated the first separate judgment

Public shared function isemptytext (byval objs as form) as Boolean for each objcon as control in objs. controls if (typeof objcon is textbox) or (typeof objcon is ComboBox) then if objcon. text. trim = "" Then msgbox (objcon. tag + "cannot be blank! ", Vbokonly + vbinformation," system prompt ") objcon. Focus () return false exit for else return true end if next end Function

Third: the second optimization solves the traversal problem.

Public shared function isemptytext (byval objs as form) as Boolean for I as integer = objs. controls. count-1 to 0 step-1 If (typeof objs. controls (I) is textbox) or (typeof objs. controls (I) is ComboBox) then if objs. controls (I ). text. trim = "" Then msgbox (objs. controls (I ). tag + "cannot be blank! ", Vbokonly + vbinformation," system prompt ") objs. Controls (I). Focus () return false exit for end if next end Function

Call Method

'Call the isemptytext () function to verify whether the form control is empty. Dim strisempty = isempty. isemptytext (me) If strisempty = true then exit sub end if

Running Effect

Maybe the code is not perfect, even if there is a ready-made one (heavyweight query control-sp1234 ). However, in the course of learning, you must first have this kind of consciousness and try to do it, whether it's learned from others or researched by yourself, then, I will gradually learn more about the previous knowledge in the future.