Andrus,

Two things to change in your code.

1) Check for DBNull.Value, not null
2) Use the TableNewRow event, not the RowChanging event

table.TableNewRow += new DataTableNewRowEventHandler(table_TableNewRow);

void table_TableNewRow(object sender, DataTableNewRowEventArgs e)
{
	string pk = e.Row.Table.PrimaryKey[0].ColumnName;
	if (e.Row[pk] == DBNull.Value)
		e.Row[pk] = new System.Guid();
}

See if that will work for you.

~~Bonnie



>I have .NET 1 WinForms dataGrid bound to dataTable.
>dataTable has primary key field.
>dataTable constraints should be checked during editing.
>
>If user moves out from new row, an error occurs.
>RowChanging event does not fire before error.
>
>How to fill field with dynamic default value when new row is added to DataGrid ?
>
>To reproduce:
>
>1. Run code
>2. Enter data to first column only
>3. Press Down Arrow
>
>Observed error:
>
>---------------------------
>Committing the row to the original data store has caused an error.
>---------------------------
>Value Column 'Column2' does not allow nulls. Do you want to correct this value?
>
>Expected:
>
>No error. Primary key column should be filled.
>
>

using System.Windows.Forms;
>using System.Data;
>static class Program {
>	static void Main() {
>		Application.Run(new Frm());
>		}
>	}
>
>class Frm: Form {
>	public Frm() {
>		DataTable table = new DataTable();
>		DataColumn[] keys = new DataColumn[1];
>		DataColumn column1 = new DataColumn();
>		DataColumn column2 = new DataColumn();
>		DataGrid grid = new DataGrid();
>		
>		grid.Dock = DockStyle.Fill;
>		table.Columns.Add(column1);
>		table.Columns.Add(column2);
>		keys[0] = column2;
>		table.PrimaryKey = keys;
>		Controls.Add(grid);
>		table.RowChanging += new DataRowChangeEventHandler(OnRowChanging);
>		grid.SetDataBinding(table, "");
>		}
>
>	private void OnRowChanging(object sender, DataRowChangeEventArgs e) {
>		if (e.Action == DataRowAction.Add) {
>			string pk = e.Row.Table.PrimaryKey[0].ColumnName;
>			if (e.Row[pk] == null)
>				e.Row[pk] = new System.Guid();
>			}
>		}
>	}
>