Procedura: formattare dati personalizzati in un controllo DataGridView di Windows Form

Nell'esempio di codice seguente viene illustrato come implementare un gestore per l'evento DataGridView.CellFormatting che modifica la visualizzazione delle celle a seconda delle colonne e dei valori.

Le celle nella colonna Balance che contengono numeri negativi hanno uno sfondo rosso. È anche possibile formattare le celle come valuta per visualizzare le parentesi intorno ai valori negativi. Per altre informazioni, vedere Procedura: Formattare i dati nel controllo DataGridView di Windows Form.

Nelle celle della colonna Priority vengono visualizzate delle immagini invece dei valori delle celle testuali corrispondenti. La proprietà Value della classe DataGridViewCellFormattingEventArgs viene usata sia per ottenere il valore della cella testuale che per impostare il valore di visualizzazione dell'immagine corrispondente.

Esempio

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

public class Form1 : Form
{
    private DataGridView dataGridView1 = new DataGridView();
    private Bitmap highPriImage;
    private Bitmap mediumPriImage;
    private Bitmap lowPriImage;

    public Form1()
    {
        // Initialize the images.
        try
        {
            highPriImage = new Bitmap("highPri.bmp");
            mediumPriImage = new Bitmap("mediumPri.bmp");
            lowPriImage = new Bitmap("lowPri.bmp");
        }
        catch (ArgumentException)
        {
            MessageBox.Show("The Priority column requires Bitmap images " +
                "named highPri.bmp, mediumPri.bmp, and lowPri.bmp " +
                "residing in the same directory as the executable file.");
        }

        // Initialize the DataGridView.
        dataGridView1.Dock = DockStyle.Fill;
        dataGridView1.AllowUserToAddRows = false;
        dataGridView1.Columns.AddRange(
            new DataGridViewTextBoxColumn(),
            new DataGridViewImageColumn());
        dataGridView1.Columns[0].Name = "Balance";
        dataGridView1.Columns[1].Name = "Priority";
        dataGridView1.Rows.Add("-100", "high");
        dataGridView1.Rows.Add("0", "medium");
        dataGridView1.Rows.Add("100", "low");
        dataGridView1.CellFormatting +=
            new System.Windows.Forms.DataGridViewCellFormattingEventHandler(
            this.dataGridView1_CellFormatting);
        this.Controls.Add(dataGridView1);
    }

    // Changes how cells are displayed depending on their columns and values.
    private void dataGridView1_CellFormatting(object sender,
        System.Windows.Forms.DataGridViewCellFormattingEventArgs e)
    {
        // Set the background to red for negative values in the Balance column.
        if (dataGridView1.Columns[e.ColumnIndex].Name.Equals("Balance"))
        {
            Int32 intValue;
            if (Int32.TryParse((String)e.Value, out intValue) &&
                (intValue < 0))
            {
                e.CellStyle.BackColor = Color.Red;
                e.CellStyle.SelectionBackColor = Color.DarkRed;
            }
        }

        // Replace string values in the Priority column with images.
        if (dataGridView1.Columns[e.ColumnIndex].Name.Equals("Priority"))
        {
            // Ensure that the value is a string.
            String stringValue = e.Value as string;
            if (stringValue == null) return;

            // Set the cell ToolTip to the text value.
            DataGridViewCell cell = dataGridView1[e.ColumnIndex, e.RowIndex];
            cell.ToolTipText = stringValue;

            // Replace the string value with the image value.
            switch (stringValue)
            {
                case "high":
                    e.Value = highPriImage;
                    break;
                case "medium":
                    e.Value = mediumPriImage;
                    break;
                case "low":
                    e.Value = lowPriImage;
                    break;
            }
        }
    }

    public static void Main()
    {
        Application.Run(new Form1());
    }
}
Imports System.Drawing
Imports System.Windows.Forms

Public Class Form1
    Inherits Form

    Private WithEvents dataGridView1 As New DataGridView()
    Private highPriImage As Bitmap
    Private mediumPriImage As Bitmap
    Private lowPriImage As Bitmap

    Public Sub New()

        ' Initialize the images. 
        Try
            highPriImage = New Bitmap("highPri.bmp")
            mediumPriImage = New Bitmap("mediumPri.bmp")
            lowPriImage = New Bitmap("lowPri.bmp")
        Catch ex As ArgumentException
            MessageBox.Show("The Priority column requires Bitmap images" & _
                "named highPri.bmp, mediumPri.bmp, and lowPri.bmp " & _
                "residing in the same directory as the executable file.")
        End Try

        ' Initialize the DataGridView.
        With dataGridView1
            .Dock = DockStyle.Fill
            .AllowUserToAddRows = False
            .Columns.AddRange( _
                New DataGridViewTextBoxColumn(), _
                New DataGridViewImageColumn())
            .Columns(0).Name = "Balance"
            .Columns(1).Name = "Priority"
            .Rows.Add("-100", "high")
            .Rows.Add("0", "medium")
            .Rows.Add("100", "low")
        End With

        Me.Controls.Add(dataGridView1)

    End Sub

    ' Changes how cells are displayed depending on their columns and values.
    Private Sub dataGridView1_CellFormatting(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) _
        Handles dataGridView1.CellFormatting

        ' Set the background to red for negative values in the Balance column.
        If dataGridView1.Columns(e.ColumnIndex).Name.Equals("Balance") Then

            'Dim intValue As Int32
            If CInt(e.Value) < 0 Then
                'if Int32.TryParse((String)e.Value, out intValue) && 
                '   (intValue < 0))

                e.CellStyle.BackColor = Color.Red
                e.CellStyle.SelectionBackColor = Color.DarkRed
            End If
        End If

        ' Replace string values in the Priority column with images.
        If dataGridView1.Columns(e.ColumnIndex).Name.Equals("Priority") Then

            ' Ensure that the value is a string.
            Dim stringValue As String = TryCast(e.Value, String)
            If stringValue Is Nothing Then Return

            ' Set the cell ToolTip to the text value.
            Dim cell As DataGridViewCell = _
                dataGridView1(e.ColumnIndex, e.RowIndex)
            cell.ToolTipText = stringValue

            ' Replace the string value with the image value.
            Select Case stringValue

                Case "high"
                    e.Value = highPriImage
                Case "medium"
                    e.Value = mediumPriImage
                Case "low"
                    e.Value = lowPriImage

            End Select

        End If

    End Sub

    Public Sub Main()
        Application.Run(New Form1())
    End Sub

End Class

Compilazione del codice

L'esempio presenta i requisiti seguenti:

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

  • Le immagini Bitmap denominate highPri.bmp, mediumPri.bmp e lowPri.bmp risiedono nella stessa directory del file eseguibile.

Vedi anche