適應文本驗證功能考慮所選文本

Question

我有這個功能，其與按鍵事件評估的文本框（或組合框或MaskedTextBox中）控制的內容，並結合地，將允許或禁止輸入端。對於只有數字輸入有效的日期或文本框非常有用。如果在函數調用中指定，它允許一位小數點後的一組數字。如果文本框已滿，它也允許退格字符。

我希望它允許我輸入什麼，否則將有效的文本時，文本框已滿，但一個或多個字符突出顯示（因此將被按鍵字符替換。任何人都可以告訴我如何做到這一點好嗎？

''' <summary> 
''' Validates that input is numeric. 
''' Allows one decimal place unless intDecimal is less than 1 
''' Will allow a set number of numbers after the decimal place. 
''' </summary> 
''' <param name="strKeyPress">The key which has been pressed</param> 
''' <param name="strText">Current text of the textbox</param> 
''' <param name="intPosition">Current cursor position in textbox</param> 
''' <param name="intDecimal">Number of decimal places desired.</param> 
''' <returns>Boolean: true means that input is numeric, false means it is not.</returns> 
''' <remarks>Used with a keypress event to validate input. Do not handle input if function returns false.</remarks> 
Public Function InputIsNumeric(ByVal strKeyPress As String, ByVal strText As String, ByVal intPosition As Integer, ByVal intDecimal As Integer) As Boolean 
    Dim dot As Integer 
    Dim ch As String 
    Dim returnValue As Boolean 

    If Not Char.IsDigit(CType(strKeyPress, Char)) Then returnValue = True 
    If strKeyPress = "-" And intPosition = 0 Then returnValue = False 'allow negative number 
    If strKeyPress = "." And strText.IndexOf(".") = -1 And intDecimal > 0 Then returnValue = False 'allow single decimal point 
    dot = strText.IndexOf(".") 
    If dot > -1 Then 'limit to set decimal places 
     ch = strText.Substring(dot + 1) 
     If ch.Length > (intDecimal - 1) Then returnValue = True 
    End If 
    If strKeyPress = Chr(8) Then returnValue = False 'allow Backspace 
    Return returnValue 
End Function 

Answer 1

您可以添加幾個參數（intLengthOfHighlightedText和intLengthOfControl），並通過Textbox.SelectedText和TextboxName.MaxLength（假設單行文本控件）。然後，只需工作是出在你的功能，否則你可以通過整個文本框控件的值（使它超載或組合框等做的工作）。