【WinForm窗体控件开发】之二 简单的窗体控件
我们做一个简单的例子：
下面是继承自Control类的自定义窗体控件的代码：
FirstControl继承控件代码
using
System.ComponentModel;
using
System.Drawing;
using
System.Windows.Forms;
namespace
之二简单的窗体控件Demo
{
public
class
FirstControl:Control
{
///
<summary>
///
Constructor
///
</summary>
public
FirstControl() { }
#region
FirstControl 使用该属性来设置从 Control 继承的 Text 属性的显示格式
//
ContentAlignment is an enumeration defined in the System.Drawing
//
namespace that specifies the alignment of content on a drawing
//
surface.
private
ContentAlignment alignmentValue
=
ContentAlignment.MiddleLeft;
[
Category(
"
Alignment
"
),
Description(
"
Specifies the alignment of text.
"
)
]
public
ContentAlignment TextAlignment
{
get
{
return
alignmentValue;
}
set
{
alignmentValue
=
value;
//
The Invalidate method invokes the OnPaint method described
//
in step 3.
//
在设置更改控件可视显示的属性时，必须调用 Invalidate 方法来重新绘制该控件。
//
Invalidate 是在 Control 基类中定义的。
Invalidate();
}
}
#endregion
///
<summary>
///
重写从 Control 继承的受保护的 OnPaint 方法，以便为控件提供呈现逻辑。
///
如果不改写 OnPaint，您的控件将无法自行绘制。
///
在下面的代码片段中，OnPaint 方法显示从 Control 继承的 Text 属性，并使用 alignmentValue 字段指定的对齐方式。
///
</summary>
protected
override
void
OnPaint(PaintEventArgs e)
{
base
.OnPaint(e);
StringFormat style
=
new
StringFormat();
style.Alignment
=
StringAlignment.Near;
switch
(alignmentValue)
{
case
ContentAlignment.MiddleLeft:
style.Alignment
=
StringAlignment.Near;
break
;
case
ContentAlignment.MiddleRight:
style.Alignment
=
StringAlignment.Far;
break
;
case
ContentAlignment.MiddleCenter:
style.Alignment
=
StringAlignment.Center;
break
;
}
//
Call the DrawString method of the System.Drawing class to write text.
//
Text and ClientRectangle are properties inherited from Control.
e.Graphics.DrawString(
Text,
Font,
new
SolidBrush(ForeColor),
ClientRectangle, style);
}
}
}
窗体代码：
namespace
之二简单的窗体控件Demo
{
partial
class
Form1
{
///
<summary>
///
Required designer variable.
///
</summary>
private
System.ComponentModel.IContainer components
=
null
;
///
<summary>
///
Clean up any resources being used.
///
</summary>
///
<param name="disposing">
true if managed resources should be disposed; otherwise, false.
</param>
protected
override
void
Dispose(
bool
disposing)
{
if
(disposing
&&
(components
!=
null
))
{
components.Dispose();
}
base
.Dispose(disposing);
}
#region
Windows Form Designer generated code
///
<summary>
///
Required method for Designer support - do not modify
///
the contents of this method with the code editor.
///
</summary>
private
void
InitializeComponent()
{
this
.firstControl1
=
new
之二简单的窗体控件Demo.FirstControl();
this
.firstControl2
=
new
之二简单的窗体控件Demo.FirstControl();
this
.firstControl3
=
new
之二简单的窗体控件Demo.FirstControl();
this
.SuspendLayout();
//
//
firstControl1
//
this
.firstControl1.Location
=
new
System.Drawing.Point(
12
,
24
);
this
.firstControl1.Name
=
"
firstControl1
"
;
this
.firstControl1.Size
=
new
System.Drawing.Size(
122
,
21
);
this
.firstControl1.TabIndex
=
0
;
this
.firstControl1.Text
=
"
firstControl1
"
;
this
.firstControl1.TextAlignment
=
System.Drawing.ContentAlignment.MiddleLeft;
//
//
firstControl2
//
this
.firstControl2.Location
=
new
System.Drawing.Point(
12
,
51
);
this
.firstControl2.Name
=
"
firstControl2
"
;
this
.firstControl2.Size
=
new
System.Drawing.Size(
122
,
23
);
this
.firstControl2.TabIndex
=
1
;
this
.firstControl2.Text
=
"
firstControl2
"
;
this
.firstControl2.TextAlignment
=
System.Drawing.ContentAlignment.MiddleCenter;
//
//
firstControl3
//
this
.firstControl3.Location
=
new
System.Drawing.Point(
12
,
80
);
this
.firstControl3.Name
=
"
firstControl3
"
;
this
.firstControl3.Size
=
new
System.Drawing.Size(
122
,
23
);
this
.firstControl3.TabIndex
=
2
;
this
.firstControl3.Text
=
"
firstControl3
"
;
this
.firstControl3.TextAlignment
=
System.Drawing.ContentAlignment.MiddleRight;
//
//
Form1
//
this
.AutoScaleDimensions
=
new
System.Drawing.SizeF(6F, 12F);
this
.AutoScaleMode
=
System.Windows.Forms.AutoScaleMode.Font;
this
.ClientSize
=
new
System.Drawing.Size(
214
,
182
);
this
.Controls.Add(
this
.firstControl3);
this
.Controls.Add(
this
.firstControl2);
this
.Controls.Add(
this
.firstControl1);
this
.Name
=
"
Form1
"
;
this
.Text
=
"
Form1
"
;
this
.Load
+=
new
System.EventHandler(
this
.Form1_Load);
this
.ResumeLayout(
false
);
}
#endregion
private
FirstControl firstControl1;
private
FirstControl firstControl2;
private
FirstControl firstControl3;
}
}
效果图：
控件编译后会在Toolbox工具箱中出现一个齿轮样子的小工具，直接在Form窗体上使用即可；
注意属性栏中最下面一个TextAligment属性，这是我们自己为FirstControl控件添加的属性
关于控件的常用的Attribute的详细介绍我们在下一节中进行详细介绍。