Slow TreeView node label rename

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C#

for(int i =0;i<400;i++)
{
     treeNodes[i].Text = name;
     treeNodes[i].group[i].BackColor = Color.LightBlue;
}

This loop can take my computer up to 2 minutes. But removing the label rename removes all the lag.

for(int i =0;i<400;i++)
{
     //treeNodes[i].Text = name;
     treeNodes[i].group[i].BackColor = Color.LightBlue;
}

Any clue why 400 label renames should bog the system down and how do I fix it?

________________

It is a winform so all I needed to do was

treeView1.BeginUpdate();
//tree editing stuff
treeView1.EndUpdate();

This removed all lag. Thanks!