<p>I populated a datagridview from a datatable. How do I read from the datagridview when the application is running?</p>

how did you populate it? is the DataSource something useful like a BindlingList? 
If it is then something like:
```
```
BindingSource bindingSource = this.dataGridView1.DataSource as BindingSource;
//substitute your business object type for T 
T entity = bindingSource.Current as T;
```
```
would get you the entity bound to the row.
Otherwise there is always the datagridview.Columns[n].Cells[n].Value but really I'd look at using the objects in the DataSource
Edit: Ah... a datatable... righto:
```
```
var table = dataGridView1.DataSource as DataTable;

 foreach(DataRow row in table.Rows)
 {
     foreach(DataColumn column in table.Columns)
     {
         Console.WriteLine(row[column]);
     }
 }
```
```