```
foreach (Control c in panPrev.Controls)
{
if (c.Tag == "move")

```

works well, but produce a warning: *Possible unintended reference comparison; to get a value comparison, cast the left hand side to type 'string'*

```
foreach (Control c in panPrev.Controls)
{
if (c.Tag.ToString() == "move")  // this produce NullReferenceException.

```

What to do?