Datagridview rowvalidating cancel
Dim index As Integer ' find the location of the column index = Data Grid View1. Mask = "####" ' this mask will allow only numbers (max of 4) dgv Masked Edit.
Validating Type = Get Type(Integer) dgv Masked Edit. Data Property Name = "Units In Stock" ' some more tweaking dgv Masked Edit. Automatic ' insert the new column at the same location Data Grid View1. Insert(index, dgv Masked Edit) Now the user will only be able to type numbers into this column.
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This technique provides an enhancement to the Data Grid View control that further affirms the notion that you should always attempt to prevent user input errors rather than just detect them.
This custom Data Grid View column control is contained in 3 classes...
Not only does this look better, it also prevents the user from selecting a value that would violate the foreign key constraint (meaning, you can't select a numeric value that doesn't exist in the related table) Take a look at the following example that replaces a numeric "Category ID" value with the associated user-friendly "Category" string from another table (called "Categories"). Columns("Category ID")) ' remove the existing column Data Grid View1. Remove At(index) ' create a new combobox column that we use as a "lookup" Dim dgvc As New Data Grid View Combo Box Column dgvc.
The Data Grid View is a very powerful windows form control for providing a user interface to tabular data.Cell Template End Get Set(By Val value As Data Grid View Cell) ' Ensure that the cell used for the template is a Masked Edit Cell If Not (value Is Nothing) And Not value. Is Assignable From( _ Get Type(Data Grid View Masked Edit Cell)) Then Throw New Invalid Cast Exception("Must be a Data Grid View Masked Edit Cell") End If My Base. It inherits from the Masked Text Box control (to get the user interface we want) and implements the Editing Control interface so that the control works inside the Data Grid View. Editing Control Row Index Get Return row Index Num End Get Set(By Val value As Integer) row Index Num = value End Set End Property Public Function Editing Control Wants Input Key(By Val key As Keys, By Val _ data Grid View Wants Input Key As Boolean) As Boolean Implements _ IData Grid View Editing Control.Cell Template = value End Set End Property ' ' New properties required by the Masked Text Box control ' Public Property Mask() As String Get Return p Mask End Get Set(By Val value As String) p Mask = value End Set End Property Public Property Prompt Char() As Char Get Return p Prompt Char End Get Set(By Val value As Char) p Prompt Char = value End Set End Property Public Property Validating Type() As Type Get Return p Validating Type End Get Set(By Val value As Type) p Validating Type = value End Set End Property End Class The next step is the Masked Edit Cell class. Most of the code required to implement the methods and properties is fairly straight forward. Editing Control Wants Input Key Return True End Function Public Sub Prepare Editing Control For Edit(By Val select All As Boolean) Implements _ IData Grid View Editing Control.' Private Sub Data Grid View1_Row Validating(By Val sender As Object, By Val e As _ System. Row Validating ' Assume that text input is complete when you attempt to navigate ' away from the row Data Grid View1. In this case we're just checking to ' see if the Unit Price is a positive number If Data Grid View1. Luckily, the Data Grid View Combo Box Column control was designed to help solve this problem.You can use a Data Grid View Combo Box Column to act a as "look up table" to show a user friendly version of the field, rather than just a numeric equivalent.
Public Class Data Grid View Masked Edit Column Inherits Data Grid View Column Private p Prompt Char As Char = "_"c Private p Validating Type As Type = Get Type(String) Private p Mask As String = "" Public Sub New() My Base. Prompt Char End Sub Public Overrides Read Only Property Edit Type() As Type Get ' Return the type of the editing control that Masked Edit Editing Control uses.