<script language="javascript" type="text/javascript">
     function client_OnTreeNodeChecked()
     {
         var obj = window.event.srcElement;
         var treeNodeFound = false;
         var checkedState;
         if (obj.tagName == "INPUT" && obj.type == "checkbox")
         {
             var treeNode = obj;
             checkedState = treeNode.checked;
                do
                {
                    obj = obj.parentElement;
                }
                
                while (obj.tagName != "TABLE")
                var parentTreeLevel = obj.rows[0].cells.length;
                var parentTreeNode = obj.rows[0].cells[0];
                var tables = obj.parentElement.getElementsByTagName("TABLE");
                var numTables = tables.length
                if (numTables >= 1)
                {
                    for (i=0; i < numTables; i++)
                    {
                        if (tables[i] == obj)
                        {
                            treeNodeFound = true;
                            i++;
                            if (i == numTables)
                            {
                                return;
                            }
                        }
                        if (treeNodeFound == true)
                        {
                            var childTreeLevel = tables[i].rows[0].cells.length;
                            if (childTreeLevel > parentTreeLevel)
                            {
                                var cell = tables[i].rows[0].cells[childTreeLevel - 1];
                                var inputs = cell.getElementsByTagName("INPUT");
                                inputs[0].checked = checkedState;
                            }
                            else
                            {
                                return;
                            }
                        }
                    }
              }
        }
    }   
    </script>

------解决方案--------------------

探讨

根节点只有一个，那我只想让这个根节点的第一个子节点被选上


------解决方案--------------------
探讨


引用:
根节点只有一个，那我只想让这个根节点的第一个子节点被选上

如果是这样的话，以下是不是楼主的意思：
        TreeView1.Nodes[0].Expand();
       TreeView1.Nodes[0].ChildNodes[0].Selected = true;


------解决方案--------------------
TreeView1.Nodes[0].Expand();
TreeView1.Nodes.Selected .clear();
TreeView1.Nodes[0].ChildNodes[0].Selected = true;