Display GridError

Question

DataTable dt = new DataTable();

dt.Columns.Add("ItemRowId", typeof(int));

dt.Columns.Add("ItemCode", typeof(string));

dt.Columns.Add("ItemName", typeof(string));

dt.Columns.Add("MRP", typeof(float));

dt.Columns.Add("tur", typeof(float));

dt.Columns.Add("UPC", typeof(float));

foreach (GridViewRow row in xdata.Rows)

{

if (row.RowType == DataControlRowType.DataRow)

{

CheckBox chkSelect = (row.Cells[0].FindControl("chkSelect") as CheckBox);

if (chkSelect.Checked)

{

int ItemRowId = int.Parse(row.Cells[1].Text);

string ItemCode = row.Cells[2].Text;

string ItemName = row.Cells[3].Text;

float MRP = float.Parse(row.Cells[4].Text);

float tur = float.Parse(row.Cells[5].Text);

float UPC = float.Parse(row.Cells[6].Text);

dt.Rows.Add(ItemRowId, ItemCode, ItemName, MRP, tur);

}

}

}

Session.Add("dtgetselectedRecords", dt);

Server.Transfer("~/Grid2.aspx");

 

It is in float format and it accepts null values.  

showing error :  input string was not in correct format