C#实现自定义圆角按钮的方法

winform中自带的button没有圆角属性，所以我们继承button类，重写onpaint事件来绘制圆角按钮。

1.绘制圆角按钮框需要用到系统自带的绘制方法：首先引入gdi32.dll中的createroundrectrgn方法。经过验证此方法在大量控件情况下使用，会导致gdi+绘图问题！现在改用自己绘制的圆角graphicspath进行填充显示，效果更好，圆角更圆润了！

重写onpaint方法：

protected override void onpaint(painteventargs pe)
        {
            if (!roundcorner)
            {
                base.onpaint(pe);
                return;
            }
            graphics g = pe.graphics;
            g.smoothingmode = smoothingmode.antialias;
            //g.smoothingmode = smoothingmode.highquality;
            //g.compositingquality = compositingquality.highquality;
            //g.interpolationmode = interpolationmode.highqualitybicubic;
            rectangle rect = this.clientrectangle;
            brush brhborder = new solidbrush(crborderpainting);
            brush brhrect = new solidbrush(backcolor);
            brush b0 = new solidbrush(this.parent.backcolor);
            brush bfont = new solidbrush(forecolor);
            try
            {
                g.clear(this.parent.backcolor);
                int bordersize = flatappearance.bordersize;
                try
                {
                    graphicspath path = createroundrect(rect.left, rect.top, rect.left + rect.width - bordersize, rect.top + rect.height - bordersize);
                    g.fillpath(brhborder, path);
                    path.dispose();
                    path = createroundrect(rect.left + bordersize /2f, rect.top + bordersize / 2f, rect.left + rect.width - bordersize * 2, rect.top + rect.height - bordersize * 2);
                    g.fillpath(brhrect, path);
                    path.dispose();
                }
                catch (exception e)
                {
                    console.writeline("fillpath:" + e.message);
                }
                if (this.text != string.empty)
                {
                    stringformat sf = stringformat.generictypographic;
                    sf.formatflags |= stringformatflags.measuretrailingspaces;
                    sizef sizeoftext = g.measurestring(this.text, font);
                    float tx = (float)((this.width - sizeoftext.width) / 2.0);
                    float ty = (float)((this.height - sizeoftext.height) / 2.0);
                    g.drawstring(this.text, font, bfont, tx, ty);
                }
            }
            finally
            {
                b0.dispose();
                brhborder.dispose();
                brhrect.dispose();
                bfont.dispose();
            }
        }

private graphicspath createroundrect(float rleft, float rtop, float rwidth, float rheight)
        {
            float r = radius;
            if (rwidth < rheight)
            {
                if (radius > rwidth / 2f)
                    r = rwidth / 2f;
            }
            else
            {
                if (radius > rheight / 2f)
                    r = rheight / 2f;
            }

            graphicspath path;
            rectanglef rectrow = new rectanglef(rleft, rtop + r, rwidth, rheight - r * 2);
            rectanglef rectcolumn = new rectanglef(rleft + r, rtop, rwidth - r * 2, rheight);
            path = new graphicspath(fillmode.winding);
            path.addrectangle(rectrow);
            path.addrectangle(rectcolumn);
            //左上
            path.addellipse(rleft, rtop, r * 2, r * 2);
            //右上
            path.addellipse(rleft + rwidth - r * 2, rtop, r * 2, r * 2);
            //左下
            path.addellipse(rleft, rtop + rheight - r * 2, r * 2, r * 2);
            //右下
            path.addellipse(rleft + rwidth - r * 2, rtop + rheight - r * 2, r * 2, r * 2);
            return path;
        }

2.如果需要增加悬浮效果，可以重写onmouseenter、onmouseleave事件来改变边界及背景色。

private color crborderactive = color.fromargb(convert.toint32("ff3283c4", 16));
private color crrectactive = color.fromargb(convert.toint32("ffe3f3fb", 16));
private color crborderdefault = color.fromargb(215, 215, 215);
protected override void onmouseenter(eventargs e)
        {
            base.onmouseenter(e);
            this.backcolor = crrectactive;
            this.flatappearance.bordercolor = crborderactive;
        }
        protected override void onmouseleave(eventargs e)
        {
            base.onmouseleave(e);
            this.backcolor = color.white;
            this.flatappearance.bordercolor = crborderdefault;
        }

至此一个圆角按钮就完成了^_^。效果如下：

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