上下按键寻找文本框中输入的匹配项

void txtDatumName_TextChanged(object sender, EventArgs e)
        {
           
            strDatumName = this.txtDatumName.Text.Trim();
            if (!string.IsNullOrEmpty(strDatumName))
            {
                foreach (ListViewItem item in this.datumCategoriesList.Items)
                {
                    if (item.SubItems[1].Text.Contains(strDatumName))
                    {
                        datumCategoriesList.Items[0].Selected = true;
                        item.Selected = true;
                        this.datumCategoriesList.EnsureVisible(item.Index);
                        break;
                    }
                    else
                    {
                        datumCategoriesList.SelectedItems.Clear();
                    }
                }
            }
            //文本框什么都不存在的时候就不会选中listview
            else
            {
                datumCategoriesList.SelectedItems.Clear();
            }
        }

this.txtDatumName.KeyDown+=txtDatumName_KeyDown;

//添加按向上向下箭头进行切换listview的事件
        private void txtDatumName_KeyDown(object sender, KeyEventArgs e)
        {
            //临时的listview对象
            ListViewItem itemCode = null;

            #region 文本框存在内容时才会执行
            if (e.KeyCode == Keys.Down)
            {
                if (itemCode != null)
                {
                    //循环去查找符合strDatumName内容要求的项，从临时的listview对象存储的这一项开始查找
                    for (int i = itemCode.Index; i < datumCategoriesList.Items.Count; i++)
                    {
                        //如果TXT文本框包含这一项
                        if (datumCategoriesList.Items[i].SubItems[1].Text.Contains(strDatumName))
                        {
                            //找距离当前一个最近的前一个项
                            if (datumCategoriesList.Items[i].Index > datumCategoriesList.SelectedItems[0].Index)
                            {
                                datumCategoriesList.Items[i].Selected = true;
                                this.datumCategoriesList.EnsureVisible(datumCategoriesList.Items[i].Index);
                                //当前选中行的值赋给一个临时的listview下次查找就从这个新的listview的位置开始查找
                                itemCode = datumCategoriesList.Items[datumCategoriesList.SelectedItems[0].Index];
                                break;
                            }
                        }
                        else
                        {
                            datumCategoriesList.Items[i].Selected = false;
                        }
                    }
                }
                else
                {
                    for (int i = 0; i < datumCategoriesList.Items.Count; i++)
                    {
                        if (datumCategoriesList.Items[i].SubItems[1].Text.Contains(strDatumName))
                        {
                            if (datumCategoriesList.Items[i].Index > datumCategoriesList.SelectedItems[0].Index)
                            {
                                datumCategoriesList.Items[i].Selected = true;
                                this.datumCategoriesList.EnsureVisible(datumCategoriesList.Items[i].Index);
                                //当前选中行的值赋给一个临时的listview下次查找就从这个新的listview的位置开始查找
                                itemCode = datumCategoriesList.Items[datumCategoriesList.SelectedItems[0].Index];
                                break;
                            }
                        }
                        else
                        {
                            datumCategoriesList.Items[i].Selected = false;
                        }
                    }
                }
            }
            else if (e.KeyCode == Keys.Up)
            {

                if (itemCode != null)
                {
                    for (int i = datumCategoriesList.Items.Count - 1; i >= itemCode.Index; i--)
                    {
                        //如果TXT文本框包含这一项
                        if (datumCategoriesList.Items[i].SubItems[1].Text.Contains(strDatumName))
                        {
                            //找距离当前一个最近的前一个项
                            if (datumCategoriesList.Items[i].Index < datumCategoriesList.SelectedItems[0].Index)
                            {
                                datumCategoriesList.Items[i].Selected = true;
                                this.datumCategoriesList.EnsureVisible(datumCategoriesList.Items[i].Index);
                                //当前选中行的值赋给一个临时的listview下次查找就从这个新的listview的位置开始查找
                                itemCode = datumCategoriesList.Items[datumCategoriesList.SelectedItems[0].Index];
                                break;
                            }
                        }
                        else
                        {
                            datumCategoriesList.Items[i].Selected = false;
                        }
                    }

                }
                else
                {
                    for (int i = datumCategoriesList.Items.Count - 1; i >= 0; i--)
                    {
                        //如果TXT文本框包含这一项
                        if (datumCategoriesList.Items[i].SubItems[1].Text.Contains(strDatumName))
                        {
                            //找距离当前一个最近的前一个项
                            if (datumCategoriesList.Items[i].Index < datumCategoriesList.SelectedItems[0].Index)
                            {
                                datumCategoriesList.Items[i].Selected = true;
                                this.datumCategoriesList.EnsureVisible(datumCategoriesList.Items[i].Index);
                                //当前选中行的值赋给一个临时的listview下次查找就从这个新的listview的位置开始查找
                                itemCode = datumCategoriesList.Items[datumCategoriesList.SelectedItems[0].Index];
                                break;
                            }
                        }
                        else
                        {
                            datumCategoriesList.Items[i].Selected = false;
                        }
                    }
                }
            }
            e.Handled = true; 
            #endregion
        }

 其中，datumCategoriesList.Items[i].SubItems[1].Text表示获取listview的选中行的值