An earlier post dealt with creating a GridView programmatically. In some cases, this GridView might need to be used multiple times throughout a site, either using the same data, or perhaps a different set of data. Several options exist when determining how to implement this.
The simplest, of course, would be simply to copy the code and then make changes in each copy as needed. This clearly violates the DRY principle, and will only lead to heartache (and possibly carpal tunnel syndrome) in the long run. As soon as the customer wants the look and feel of the GridView to change, you would have to change each instance where the code was copied.
The second, and slightly more desirable option, would be to refactor this code into a method that creates the GridView by calling the method. While this is much preferable to having 20 verbatim copies of code in your site, it’s still not ideal. This methodology contributes to spaghetti programming, and should be avoided when feasible.
The ideal method is to create an object that inherits from the GridView class, and then setting the attributes in the object. Once the object is instantiated, any attributes that need to be added or overridden can be at runtime, prior to a databind event.
Here is an example of a class that inherits from GridView:
Public Class MyGridView Inherits System.Web.UI.WebControls.GridView Public Sub New(ByVal strID As String) ID = strID CssClass = "gridview" AutoGenerateColumns = False CellPadding = 4 DataKeyNames = New String() {"ExampleID"} ForeColor = Drawing.ColorTranslator.FromHtml("#2a2723") GridLines = GridLines.None Width = Unit.Percentage(100) AllowSorting = True AllowPaging = False Dim strHeadBack As String = "#ffcb00" Dim strPagerBack As String = "#009ddb" Dim strForeColor As String = "#000000" HeaderStyle.BackColor = Drawing.ColorTranslator.FromHtml(strHeadBack) HeaderStyle.Font.Bold = True HeaderStyle.ForeColor = Drawing.ColorTranslator.FromHtml(strForeColor) RowStyle.BackColor = Drawing.ColorTranslator.FromHtml("#FFFBD6") RowStyle.ForeColor = Drawing.ColorTranslator.FromHtml("#2a2723") RowStyle.HorizontalAlign = HorizontalAlign.Center AlternatingRowStyle.BackColor = Drawing.Color.White BorderColor = Drawing.ColorTranslator.FromHtml("#d80073") BorderStyle = BorderStyle.Groove Dim ViewButton As New ButtonField ViewButton.HeaderText = "View" ViewButton.ButtonType = ButtonType.Button ViewButton.Text = "View" ViewButton.CommandName = "ViewExample" Columns.Add(ViewButton) Dim EditButton As New TemplateField EditButton.HeaderText = "Edit" EditButton.ItemTemplate = New MyButtonTemplate ' This is a user-defined class that creates this Button EditButton.Visible = bEditVisible Columns.Add(EditButton) Dim Voided As New CheckBoxField Voided.HeaderText = "Voided" Voided.DataField = "Voided" Voided.ReadOnly = True Voided.Visible = bVoidVisible Columns.Add(Voided) Dim ExampleDate As New TemplateField ExampleDate.HeaderText = "Date/Time" ExampleDate.SortExpression = "Date_and_Time" ExampleDate.ItemTemplate = New MyLabelTemplate ' This is a user-defined class that creates this Label ExampleDate.ItemStyle.Wrap = False Columns.Add(ExampleDate) Dim ShortColumn As New BoundField ShortColumn.ItemStyle.CssClass = "left" ShortColumn.HeaderText = "Short Column" ShortColumn.SortExpression = "Short_Column" ShortColumn.DataField = "Short_Column" ShortColumn.ItemStyle.Wrap = True ShortColumn.ItemStyle.Width = 150 Columns.Add(ShortColumn) Dim LongColumn As New BoundField LongColumn.ItemStyle.CssClass = "left" LongColumn.HeaderText = "Long Column" LongColumn.SortExpression = "Long_Column" LongColumn.DataField = "Long_Column" LongColumn.ItemStyle.HorizontalAlign = HorizontalAlign.Left LongColumn.ItemStyle.Wrap = True LongColumn.ItemStyle.Width = 200 Columns.Add(LongColumn) Dim CreatedBy As New BoundField CreatedBy.HeaderText = "Created By" CreatedBy.SortExpression = "CreatedBy" CreatedBy.DataField = "CreatedBy" Columns.Add(CreatedBy) End Sub End Class
To instantiate the object, simply declare the GridView as “MyGridView”, as below:
Private WithEvents gv1 As New MyGridView("gv1") '... gv1.DataSource = dvDataView 'A previously defined DataView '...any other attributes to be added or overridden ' To remove a column use: gv1.Columns.RemoveAt(x) ' where x is the index of the column ' Bind the data to the GridView gv1.DataBind() phPlaceHolder.Controls.Add(gv1)
And that’s it! The custom GridView is like any other GridView; DataBind() can be called to rebind data, it can be hidden or made visible, etc.
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