I need to edit the text of a DataGridViewCell. To be specific, I need to change the text from `-1` to `"N/A"`

First I tried this:

```
dgResults.Rows[0].Cells[0].Value = "N/A";

```

But it complained at runtime:

![enter image description here](https://i.stack.imgur.com/SUMuP.png)

After that, I tried changing the datatype of the column:

```
dTable.Columns[0].DataType = System.Type.GetType("System.String");  

```

and I get this error:

```
Cannot change DataType of a column once it has data.

```

I have no access to the database and cannot modify it.