| 发表于：2007-03-02 23:14:42 楼主 |
private datatable mydatatable;
private void run（)//测试函数
{
mydatatable=new datatable（ "namestable ");
mydatatable.columns.add（new datacolumn（ "name "));
mydatatable.columns.add（new datacolumn（ "inf "));
dataset ds=new dataset（);
ds.tables.add（mydatatable);
datagrid1.datasource=ds;
datagrid1.datamember= "namestable ";
addgridstyle（);
adddata（);
}
private void addgridstyle（)
{
datagridtablestyle mygridstyle=new datagridtablestyle（);
mygridstyle.mappingname= "namestable ";
datagridtextboxcolumn namecolumn=new datagridtextboxcolumn（);
namecolumn.mappingname= "name ";
namecolumn.headertext= "inf ";
mygridstyle.gridcolumnstyles.add（namecolumn);
//dategridcomboboxculumn comboboxcolumnstyle=new dategridcomboboxculumn（);
datagridcolumnstyle comboboxcolumnstyle=new dategridcomboboxculumn（);
comboboxcolumnstyle.mappingname= "inf ";
comboboxcolumnstyle.headertext= "inf ";
comboboxcolumnstyle.width=100;
mygridstyle.gridcolumnstyles.add（comboboxcolumnstyle);
datagrid1.tablestyles.add（mygridstyle);
}
private void adddata（)
{
datarow drow=mydatatable.newrow（);
drow[ "name "]= "name 1 ";
drow[ "inf "]= "tsm ";
mydatatable.rows.add（drow);
drow=mydatatable.newrow（);
drow[ "name "]= "name 2 ";
drow[ "inf "]= "zl ";
mydatatable.rows.add（drow);
drow=mydatatable.newrow（);
drow[ "name "]= "name 3 ";
drow[ "inf "]= "wb ";
mydatatable.rows.add（drow);
mydatatable.acceptchanges（);
}
}
public class dategridcomboboxculumn : datagridcolumnstyle
{
private combobox mycombobox=new combobox（);
private bool isediting;
public dategridcomboboxculumn（) : base（)
{
mycombobox.visible=false;
mycombobox.text= " ";
mycombobox.items.add（ "tsm ");
mycombobox.items.add（ "zl ");
mycombobox.items.add（ "wb ");
}
protected override void abort（int rownum)
{
isediting=false;
//是否增加一个事件委托
mycombobox.click-=new eventhandler（mycomboboxtextchanged);
invalidate（);
}
protected override bool commit（currencymanager datasource, int rownum)
{
mycombobox.bounds=rectangle.empty;
mycombobox.click-=new eventhandler（mycomboboxtextchanged);
if（!isediting)
return false;
try
{
string strvalue=mycombobox.text;
setcolumnvalueatrow（datasource,rownum,strvalue);
}
catch
{
abort（rownum);
return false;
}
invalidate（);
return true;
}
protected override void edit（currencymanager source, int rownum, rectangle bounds, bool readonly, string instanttext, bool cellisvisible)
{
string strvalue=（string)getcolumnvalueatrow（source,rownum);
if（cellisvisible)
{
mycombobox.bounds=new rectangle（bounds.x+2,bounds.y+2,bounds.width-4,bounds.height-4);
mycombobox.text =strvalue;
mycombobox.visible=true;
mycombobox.click+=new eventhandler（mycomboboxtextchanged);
}
else
{
mycombobox.text =strvalue;
mycombobox.visible =false;
}
if（mycombobox.visible)
datagridtablestyle.datagrid.invalidate（bounds);
}
protected override size getpreferredsize（graphics g, object value)
{
return new size （100,mycombobox.preferredheight+2);
}
protected override int getminimumheight（)
{
return mycombobox.preferredheight + 2;
}
protected override int getpreferredheight（graphics g, object value)
{
return mycombobox.preferredheight+2;
}
//重载之一，一个简单的版本，其他没有涉及到的参数采用了默认值
protected override void paint（graphics g,
rectangle bounds,
currencymanager source,
int rownum)
{
paint（g, bounds, source, rownum, false);
}
//重载之二，一个简单的版本，其他没有涉及到的参数采用了默认值
protected override void paint（
graphics g,
rectangle bounds,
currencymanager source,
int rownum,
bool aligntoright)
{
paint（
g,bounds,
source,
rownum,
brushes.red,
brushes.blue,
aligntoright);
}
protected override void paint（
graphics g,
rectangle bounds,
currencymanager source,
int rownum,
brush backbrush,
brush forebrush,
bool aligntoright)
{
string strvalue=（string)getcolumnvalueatrow（source,rownum);
rectangle rect=bounds;
g.fillrectangle（backbrush,rect);
rect.offset（0,2);
rect.height-=2;
g.drawstring（strvalue,this.datagridtablestyle.datagrid.font,forebrush,rect);
}
protected override void setdatagridincolumn（datagrid value)
{
base.setdatagridincolumn （value);
if（mycombobox.parent!=null)
{
mycombobox.parent.controls.remove（mycombobox);
}
if（value!=null)
{
value.controls.add（mycombobox);
}
}
private void mycomboboxtextchanged（object sender,eventargs e)
{
this.isediting=true;
base.columnstartedediting（mycombobox);
}
}
}
错误:当你点击inf字段的某一项后（一定不能在combobox上选择项目,如果选择了,错误将不会发生,这也是很奇怪的地方),再点击另一个inf字段的项时,就会出现
/////////////////////////错误////////////////////////////////////
未处理的“system.nullreferenceexception”类型的异常出现在 system.windows.forms.dll 中。
其他信息: 未将对象引用设置到对象的实例
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怀疑dategridcomboboxculumn 的问题,但怎么也找不出 |
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