请问哪里错了？
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace Ezsoft
{
public partial class Mainfrm : Form
{
public Mainfrm()
{
InitializeComponent();
}


private void toolStripMenuItem3_Click(object sender, EventArgs e)
{

}

private void 增加业务ToolStripMenuItem_Click(object sender, EventArgs e)
{
mdichild frmmdichild = new mdichild();
frmmdichild.mdiparent = this;
frmmdichild.show();
}
}
}


错误1找不到类型或命名空间名称“mdichild”(是否缺少 using 指令或程序集引用?)E:\Program\testpro\testpro\program\Mainfrm.cs2713testpro

[解决办法]
mdichild frmmdichild = new mdichild();
这句出错了，还没有定义的吧！