Procedura: personalizzare celle e colonne nel controllo DataGridView di Windows Form estendendone il comportamento e l'aspetto

Il controllo DataGridView offre diversi metodi per personalizzare l'aspetto e il comportamento mediante proprietà, eventi e classi correlate. In alcune situazioni è possibile che i requisiti relativi alle celle non possano essere soddisfatti mediante le funzioni fornite. In questi casi per estendere le funzionalità è possibile creare una propria classe DataGridViewCell personalizzata.

La classe DataGridViewCell personalizzata può essere creata derivandola dalla classe di base DataGridViewCell o da una delle relative classi derivate. Sebbene sia possibile visualizzare qualsiasi tipo di cella in qualsiasi tipo di colonna, in genere viene creata anche una classe DataGridViewColumn personalizzata per la visualizzazione del tipo di cella. Le classi di colonna derivano da DataGridViewColumn o da uno dei tipi derivati.

Nell'esempio di codice riportato di seguito viene creata la classe di cella personalizzata DataGridViewRolloverCell in grado di rilevare il passaggio in ingresso e in uscita del mouse sui bordi delle celle. Quando il mouse è all'interno dei bordi della cella, viene disegnato un rettangolo interno. Poiché questo nuovo tipo è derivato da DataGridViewTextBoxCell, si comporta da tutti gli altri punti di vista come la classe di base. La classe di colonna correlata è DataGridViewRolloverColumn.

Per usare queste classi, creare un form contenente un controllo DataGridView, aggiungere uno o più oggetti DataGridViewRolloverColumn all'insieme Columns e popolare il controllo con righe contenenti valori.

Dato che richiede l'uso di righe non condivise, questo tipo di personalizzazione delle celle non è adatto per insiemi di dati di grandi dimensioni. Per altre informazioni sulla condivisione di righe, vedere Procedure consigliate per il ridimensionamento del controllo DataGridView Windows Form.

Per personalizzare celle e colonne nel controllo DataGridView

1. Derivare una nuova classe di cella, denominata DataGridViewRolloverCell, dal tipo DataGridViewTextBoxCell.

   public class DataGridViewRolloverCell : DataGridViewTextBoxCell
   {
   

   Public Class DataGridViewRolloverCell
       Inherits DataGridViewTextBoxCell
   

   }
   

   End Class
   

2. Eseguire l'override del metodo Paint nella classe DataGridViewRolloverCell . Eseguire l'override chiamando prima l'implementazione della classe di base, che gestisce la funzionalità della casella di testo inserita, quindi usando il metodo PointToClient del controllo per trasformare la posizione del cursore (coordinate dello schermo) nelle coordinate dell'area client DataGridView. Se le coordinate del mouse rientrano nei contorni della cella, disegnare il rettangolo interno.

   protected override void Paint(
       Graphics graphics,
       Rectangle clipBounds,
       Rectangle cellBounds,
       int rowIndex,
       DataGridViewElementStates cellState,
       object value,
       object formattedValue,
       string errorText,
       DataGridViewCellStyle cellStyle,
       DataGridViewAdvancedBorderStyle advancedBorderStyle,
       DataGridViewPaintParts paintParts)
   {
       // Call the base class method to paint the default cell appearance.
       base.Paint(graphics, clipBounds, cellBounds, rowIndex, cellState,
           value, formattedValue, errorText, cellStyle,
           advancedBorderStyle, paintParts);
   
       // Retrieve the client location of the mouse pointer.
       Point cursorPosition =
           this.DataGridView.PointToClient(Cursor.Position);
   
       // If the mouse pointer is over the current cell, draw a custom border.
       if (cellBounds.Contains(cursorPosition))
       {
           Rectangle newRect = new Rectangle(cellBounds.X + 1,
               cellBounds.Y + 1, cellBounds.Width - 4,
               cellBounds.Height - 4);
           graphics.DrawRectangle(Pens.Red, newRect);
       }
   }
   

   Protected Overrides Sub Paint( _
       ByVal graphics As Graphics, _
       ByVal clipBounds As Rectangle, _
       ByVal cellBounds As Rectangle, _
       ByVal rowIndex As Integer, _
       ByVal elementState As DataGridViewElementStates, _
       ByVal value As Object, _
       ByVal formattedValue As Object, _
       ByVal errorText As String, _
       ByVal cellStyle As DataGridViewCellStyle, _
       ByVal advancedBorderStyle As DataGridViewAdvancedBorderStyle, _
       ByVal paintParts As DataGridViewPaintParts)
   
       ' Call the base class method to paint the default cell appearance.
       MyBase.Paint(graphics, clipBounds, cellBounds, rowIndex, elementState, _
           value, formattedValue, errorText, cellStyle, _
           advancedBorderStyle, paintParts)
   
       ' Retrieve the client location of the mouse pointer.
       Dim cursorPosition As Point = _
           Me.DataGridView.PointToClient(Cursor.Position)
   
       ' If the mouse pointer is over the current cell, draw a custom border.
       If cellBounds.Contains(cursorPosition) Then
           Dim newRect As New Rectangle(cellBounds.X + 1, _
               cellBounds.Y + 1, cellBounds.Width - 4, _
               cellBounds.Height - 4)
           graphics.DrawRectangle(Pens.Red, newRect)
       End If
   
   End Sub
   

3. Eseguire l'override dei metodi OnMouseEnter e OnMouseLeave nella classe DataGridViewRolloverCell per forzare le celle a ridisegnarsi all'ingresso o all'uscita del mouse.

   // Force the cell to repaint itself when the mouse pointer enters it.
   protected override void OnMouseEnter(int rowIndex)
   {
       this.DataGridView.InvalidateCell(this);
   }
   
   // Force the cell to repaint itself when the mouse pointer leaves it.
   protected override void OnMouseLeave(int rowIndex)
   {
       this.DataGridView.InvalidateCell(this);
   }
   

   ' Force the cell to repaint itself when the mouse pointer enters it.
   Protected Overrides Sub OnMouseEnter(ByVal rowIndex As Integer)
       Me.DataGridView.InvalidateCell(Me)
   End Sub
   
   ' Force the cell to repaint itself when the mouse pointer leaves it.
   Protected Overrides Sub OnMouseLeave(ByVal rowIndex As Integer)
       Me.DataGridView.InvalidateCell(Me)
   End Sub
   

4. Derivare una nuova classe, denominata DataGridViewRolloverCellColumn, dal tipo DataGridViewColumn. Nel costruttore assegnare un nuovo oggetto DataGridViewRolloverCell alla relativa proprietà CellTemplate.

   public class DataGridViewRolloverCellColumn : DataGridViewColumn
   {
       public DataGridViewRolloverCellColumn()
       {
           this.CellTemplate = new DataGridViewRolloverCell();
       }
   }
   

   Public Class DataGridViewRolloverCellColumn
       Inherits DataGridViewColumn
   
       Public Sub New()
           Me.CellTemplate = New DataGridViewRolloverCell()
       End Sub
   
   End Class
   

Esempio

L'esempio di codice completo comprende un piccolo form di prova che illustra il comportamento del tipo di cella personalizzato.

using System;
using System.Drawing;
using System.Windows.Forms;

class Form1 : Form
{
    [STAThreadAttribute()]
    public static void Main()
    {
        Application.Run(new Form1());
    }

    public Form1()
    {
        DataGridView dataGridView1 = new DataGridView();
        DataGridViewRolloverCellColumn col =
            new DataGridViewRolloverCellColumn();
        dataGridView1.Columns.Add(col);
        dataGridView1.Rows.Add(new string[] { "" });
        dataGridView1.Rows.Add(new string[] { "" });
        dataGridView1.Rows.Add(new string[] { "" });
        dataGridView1.Rows.Add(new string[] { "" });
        this.Controls.Add(dataGridView1);
        this.Text = "DataGridView rollover-cell demo";
    }
}

public class DataGridViewRolloverCell : DataGridViewTextBoxCell
{
    protected override void Paint(
        Graphics graphics,
        Rectangle clipBounds,
        Rectangle cellBounds,
        int rowIndex,
        DataGridViewElementStates cellState,
        object value,
        object formattedValue,
        string errorText,
        DataGridViewCellStyle cellStyle,
        DataGridViewAdvancedBorderStyle advancedBorderStyle,
        DataGridViewPaintParts paintParts)
    {
        // Call the base class method to paint the default cell appearance.
        base.Paint(graphics, clipBounds, cellBounds, rowIndex, cellState,
            value, formattedValue, errorText, cellStyle,
            advancedBorderStyle, paintParts);

        // Retrieve the client location of the mouse pointer.
        Point cursorPosition =
            this.DataGridView.PointToClient(Cursor.Position);

        // If the mouse pointer is over the current cell, draw a custom border.
        if (cellBounds.Contains(cursorPosition))
        {
            Rectangle newRect = new Rectangle(cellBounds.X + 1,
                cellBounds.Y + 1, cellBounds.Width - 4,
                cellBounds.Height - 4);
            graphics.DrawRectangle(Pens.Red, newRect);
        }
    }

    // Force the cell to repaint itself when the mouse pointer enters it.
    protected override void OnMouseEnter(int rowIndex)
    {
        this.DataGridView.InvalidateCell(this);
    }

    // Force the cell to repaint itself when the mouse pointer leaves it.
    protected override void OnMouseLeave(int rowIndex)
    {
        this.DataGridView.InvalidateCell(this);
    }

}

public class DataGridViewRolloverCellColumn : DataGridViewColumn
{
    public DataGridViewRolloverCellColumn()
    {
        this.CellTemplate = new DataGridViewRolloverCell();
    }
}

Imports System.Drawing
Imports System.Windows.Forms

Class Form1
    Inherits Form

    <STAThreadAttribute()> _
    Public Shared Sub Main()
        Application.Run(New Form1())
    End Sub

    Public Sub New()
        Dim dataGridView1 As New DataGridView()
        Dim col As New DataGridViewRolloverCellColumn()
        dataGridView1.Columns.Add(col)
        dataGridView1.Rows.Add(New String() {""})
        dataGridView1.Rows.Add(New String() {""})
        dataGridView1.Rows.Add(New String() {""})
        dataGridView1.Rows.Add(New String() {""})
        Me.Controls.Add(dataGridView1)
        Me.Text = "DataGridView rollover-cell demo"
    End Sub

End Class

Public Class DataGridViewRolloverCell
    Inherits DataGridViewTextBoxCell

    Protected Overrides Sub Paint( _
        ByVal graphics As Graphics, _
        ByVal clipBounds As Rectangle, _
        ByVal cellBounds As Rectangle, _
        ByVal rowIndex As Integer, _
        ByVal elementState As DataGridViewElementStates, _
        ByVal value As Object, _
        ByVal formattedValue As Object, _
        ByVal errorText As String, _
        ByVal cellStyle As DataGridViewCellStyle, _
        ByVal advancedBorderStyle As DataGridViewAdvancedBorderStyle, _
        ByVal paintParts As DataGridViewPaintParts)

        ' Call the base class method to paint the default cell appearance.
        MyBase.Paint(graphics, clipBounds, cellBounds, rowIndex, elementState, _
            value, formattedValue, errorText, cellStyle, _
            advancedBorderStyle, paintParts)

        ' Retrieve the client location of the mouse pointer.
        Dim cursorPosition As Point = _
            Me.DataGridView.PointToClient(Cursor.Position)

        ' If the mouse pointer is over the current cell, draw a custom border.
        If cellBounds.Contains(cursorPosition) Then
            Dim newRect As New Rectangle(cellBounds.X + 1, _
                cellBounds.Y + 1, cellBounds.Width - 4, _
                cellBounds.Height - 4)
            graphics.DrawRectangle(Pens.Red, newRect)
        End If

    End Sub

    ' Force the cell to repaint itself when the mouse pointer enters it.
    Protected Overrides Sub OnMouseEnter(ByVal rowIndex As Integer)
        Me.DataGridView.InvalidateCell(Me)
    End Sub

    ' Force the cell to repaint itself when the mouse pointer leaves it.
    Protected Overrides Sub OnMouseLeave(ByVal rowIndex As Integer)
        Me.DataGridView.InvalidateCell(Me)
    End Sub

End Class

Public Class DataGridViewRolloverCellColumn
    Inherits DataGridViewColumn

    Public Sub New()
        Me.CellTemplate = New DataGridViewRolloverCell()
    End Sub

End Class

Compilazione del codice

L'esempio presenta i requisiti seguenti:

• Riferimenti agli assembly System, System.Windows.Forms e System.Drawing.

Vedi anche

• DataGridView
• DataGridViewCell
• DataGridViewColumn
• Personalizzazione del controllo DataGridView di Windows Form
• Architettura del controllo DataGridView
• Tipi di colonne nel controllo DataGridView di Windows Form
• Procedure consigliate per ridimensionare il controllo DataGridView di Windows Form