/// <summary>
/// 删除图层
/// </summary>
private void DelLayerToolStripMenuItem_Click(object sender, EventArgs e)
{
treeViewLayers.SelectedNode.ContextMenuStrip = null;
myMap.Deletelayer(treeViewLayers.SelectedNode.Index);
treeViewLayers.Nodes[0].Nodes.RemoveAt(treeViewLayers.SelectedNode.Index);
UpdateMapImg();
}