我在单元格离开时遇到自定义datagridview单元格的问题：单元格变为空白。
我有一个DataGridView，它有一些列。其中一些是标准列（datagridviewtextboxcolumn，datagridviewCheckBoxcolumn），其他是自定义的（我托管了一个自定义控件）。
想象一下以下情况：我更改自定义单元格的值，然后单击另一个标准单元格（p.e.datagridviewTextBoxcolumn）。因此，我进入标准单元格的编辑模式，但自定义单元格值变为空白。为什么？我的自定义单元格是一个图像，后跟一个文本。
更新：在整个演示中，使用datagridview中托管的自定义单元格。这是一个非常小的例子。注意PropertyEditor和PropertyEditorSource是NI的组件（NI Measurement Studio 8.6包）。也许在这里实施的是坏事？这是原因吗？
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using NationalInstruments.UI.WindowsForms;
using NationalInstruments.UI;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
this.dataGridView1.EditMode = DataGridViewEditMode.EditOnEnter;
// Creates a property editor for plot object whose property is LineStep
PropertyEditorSource propertyEditorSource = new PropertyEditorSource(new ScatterPlot(), "LineStep");
propertyEditorSource.Value = LineStep.XYStep;
PropertyEditor propertyEditor = new PropertyEditor();
propertyEditor.Source = propertyEditorSource;
//propertyEditor.SourceValue = LineStep.XYStep; // Default value for property LineStep
PropertyEditorColumn col = new PropertyEditorColumn(propertyEditor);
this.dataGridView1.Columns.Add(col);
// Creates a property editor for xycursor object whose property is Color
XYCursor xycursor = new XYCursor();
PropertyEditorSource propertyEditorSource2 = new PropertyEditorSource(xycursor, "Color");
propertyEditorSource2.Value = Color.Blue;
PropertyEditor propertyEditor2 = new PropertyEditor();
propertyEditor2.Source = propertyEditorSource2;
PropertyEditorColumn col2 = new PropertyEditorColumn(propertyEditor2);
this.dataGridView1.Columns.Add(col2);
this.dataGridView1.DataError +=new
DataGridViewDataErrorEventHandler(dataGridView1_DataError);
}
private void dataGridView1_DataError(Object sender,
DataGridViewDataErrorEventArgs e)
{
// Prevents crashing on focus lost
e.Cancel = false;
}
public class PropertyEditorColumn : DataGridViewColumn
{
#region "Necessary for design time adding columns"
private PropertyEditorSource propertyEditorSource = PropertyEditorSource.Empty;
public PropertyEditorSource PropertyEditorObject{
get { return this.propertyEditorSource; }
set { this.propertyEditorSource = value; }
}
public PropertyEditorColumn() : base(new PropertyEditorCell())
{
}
#endregion
public PropertyEditorColumn(PropertyEditor propertyEditor)
: base(new PropertyEditorCell(propertyEditor))
{
}
public override DataGridViewCell CellTemplate
{
get
{
return base.CellTemplate;
}
set
{
// Ensure that the cell used for the template is a PropertyEditorCell.
if (value != null &&
!value.GetType().IsAssignableFrom(typeof(PropertyEditorCell)))
{
throw new InvalidCastException("Must be a PropertyEditorCell");
}
base.CellTemplate = value;
}
}
}
public class PropertyEditorCell : DataGridViewTextBoxCell
{
#region "Design Time"
private PropertyEditorSource propertyEditorSource = PropertyEditorSource.Empty;
public PropertyEditorSource PropertyEditorObject2
{
get { return this.propertyEditorSource; }
set { this.propertyEditorSource = value; }
}
#endregion
public PropertyEditor propertyEditor = null;
public PropertyEditorCell() : base()
{
}
public PropertyEditorCell(PropertyEditor propertyEditor)
: this()
{
this.propertyEditor = propertyEditor;
}
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);
}
public override void InitializeEditingControl(int rowIndex,
object initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)
{
// Set the value of the editing control to the current cell value.
base.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle);
PropertyEditorEditingControl ctl = DataGridView.EditingControl as PropertyEditorEditingControl;
// Use the default row value when Value property is null.
PropertyEditorSource propertyEditorSource = (PropertyEditorSource)this.Value;
if (propertyEditorSource == null)
{
ctl.Source = (PropertyEditorSource)this.DefaultNewRowValue;
}
else
{
ctl.Source = propertyEditorSource;
}
}
public override object Clone()
{
PropertyEditorCell newCell = (PropertyEditorCell)base.Clone();
newCell.propertyEditor = this.propertyEditor;
return newCell;
}
public override Type EditType
{
get
{
// Return the type of the editing control that PropertyEditorCell uses.
return typeof(PropertyEditorEditingControl);
}
}
public override Type ValueType
{
get
{
// Return the type of the value that PropertyEditorCell contains.
return typeof(PropertyEditor);
}
}
public override object DefaultNewRowValue
{
get
{
// Use the current default value.
if (this.propertyEditor == null)
{
// Design time
return this.propertyEditorSource;
}
else
{
return this.propertyEditor.Source;
}
}
}
}
class PropertyEditorEditingControl : PropertyEditor, IDataGridViewEditingControl
{
DataGridView dataGridView;
private bool valueChanged = false;
int rowIndex;
private void EditingControlDataGridView_DataError(Object sender,
DataGridViewDataErrorEventArgs e)
{
}
public PropertyEditorEditingControl()
{
}
// Implements the IDataGridViewEditingControl.EditingControlFormattedValue
// property.
public object EditingControlFormattedValue
{
get
{
return this.Source;
}
set
{
if (value is PropertyEditorSource)
{
try
{
// This will throw an exception of the string is
// null, empty, or not in the format of a date.
this.Source = (PropertyEditorSource)value;
}
catch
{
// In the case of an exception, just use the
// default value so we're not left with a null
// value.
this.Source = PropertyEditorSource.Empty;
}
}
}
}
// Implements the
// IDataGridViewEditingControl.GetEditingControlFormattedValue method.
public object GetEditingControlFormattedValue(
DataGridViewDataErrorContexts context)
{
return EditingControlFormattedValue;
}
// Implements the
// IDataGridViewEditingControl.ApplyCellStyleToEditingControl method.
public void ApplyCellStyleToEditingControl(
DataGridViewCellStyle dataGridViewCellStyle)
{
this.Font = dataGridViewCellStyle.Font;
this.ForeColor = dataGridViewCellStyle.ForeColor;
this.BackColor = dataGridViewCellStyle.BackColor;
}
// Implements the IDataGridViewEditingControl.EditingControlRowIndex
// property.
public int EditingControlRowIndex
{
get
{
return rowIndex;
}
set
{
rowIndex = value;
}
}
// Implements the IDataGridViewEditingControl.EditingControlWantsInputKey
// method.
public bool EditingControlWantsInputKey(
Keys key, bool dataGridViewWantsInputKey)
{
// Let the DateTimePicker handle the keys listed.
switch (key & Keys.KeyCode)
{
case Keys.Left:
case Keys.Up:
case Keys.Down:
case Keys.Right:
case Keys.Home:
case Keys.End:
case Keys.PageDown:
case Keys.PageUp:
return true;
default:
return !dataGridViewWantsInputKey;
}
}
// Implements the IDataGridViewEditingControl.PrepareEditingControlForEdit
// method.
public void PrepareEditingControlForEdit(bool selectAll)
{
// No preparation needs to be done.
}
// Implements the IDataGridViewEditingControl
// .RepositionEditingControlOnValueChange property.
public bool RepositionEditingControlOnValueChange
{
get
{
return false;
}
}
// Implements the IDataGridViewEditingControl
// .EditingControlDataGridView property.
public DataGridView EditingControlDataGridView
{
get
{
return dataGridView;
}
set
{
dataGridView = value;
}
}
// Implements the IDataGridViewEditingControl
// .EditingControlValueChanged property.
public bool EditingControlValueChanged
{
get
{
return valueChanged;
}
set
{
valueChanged = value;
}
}
// Implements the IDataGridViewEditingControl
// .EditingPanelCursor property.
public System.Windows.Forms.Cursor EditingPanelCursor
{
get
{
return base.Cursor;
}
}
protected override void OnValidated(EventArgs e)
{
base.OnValidated(e);
}
protected override void OnSourceValueChanged(EventArgs e)
{
// Notify the DataGridView that the contents of the cell
// have changed.
valueChanged = true;
// below line cause app crash when focus lost so handled in dataerror event
this.EditingControlDataGridView.NotifyCurrentCellDirty(true);
base.OnSourceValueChanged(e);
}
}
}
}