Your range is only one cell. You need a range big enough to contain all the cells the list would populate.
To populate your worksheet with the list, you could do something like this.
int iRow = 0;
int iCol = 0;
if (tsm.Count() > 0)
{
foreach (var prop in tsm[0].GetType().GetProperties())
{
ws.Cells[iRow, iCol].Value = prop.Name;
iCol++;
}
iRow++;
foreach (var t in tsm)
{
iCol = 0;
foreach (var prop in t.GetType().GetProperties())
{
ws.Cells[iRow, iCol].Value = prop.GetValue(t, null);
iCol++;
}
iRow++;
}
}
If you want a range, you could add this line.
SpreadsheetGear.IRange range = ws.Cells[0, 0, iRow - 1, iCol - 1];