使用了无效参数，是什么原因？


//打印预览
public void printerView(Panel mainpanel,PictureBox[] mypb,bool rst)
{
this.currentPage = 1;
getTableValue(mainpanel,mypb);
try
{
PrintDocument pd = new PrintDocument();
pd.QueryPageSettings+= new QueryPageSettingsEventHandler(this.QueryPageSettingsEventHandler );
pd.PrintPage += new PrintPageEventHandler( this.PrintPageEventHandler);
Bitmap img=new Bitmap(mainpanel.AutoScrollMinSize.Width,mainpanel.AutoScrollMinSize.Height);
Graphics imgG=Graphics.FromImage(img);
imgG.Clear(mainpanel.BackColor);
if (rst)
{
printerp_Paint(mainpanel,new PaintEventArgs(imgG,mainpanel.ClientRectangle));
}
else
{
printer_Paint(mainpanel,new PaintEventArgs(imgG,mainpanel.ClientRectangle));
}
if ( this.storedPageSettings != null )
pd.DefaultPageSettings = this.storedPageSettings ;
PrintPreviewDialog dlg = new PrintPreviewDialog();
dlg.Document = pd;
dlg.ShowDialog();
}
运行到Bitmap img=new Bitmap(mainpanel.AutoScrollMinSize.Width,mainpanel.AutoScrollMinSize.Height);出错，是何原因？