GridView Bulk Update using check box selection

.cs file

protected void btnSearch_Click(object sender, EventArgs e)
{

BindGrid3();

}

private void BindGrid3()
{
DataSet dsErrorRecords = new DataSet();
Return returnEntity = GetErrorDetails.Get(objCurrentUser.Country, objCurrentUser.Division, txtFromDate.Text, txtToDate.Text,ddlErrorDescription.SelectedValue);
dsErrorRecords = returnEntity.ResultSet;
if(dsErrorRecords != null)
GVErrorRecords.DataSource = dsErrorRecords.Tables[0];
GVErrorRecords.DataBind();
}

protected void OnCheckedChanged(object sender, EventArgs e)
{
bool isUpdateVisible = false;

foreach (GridViewRow row in GVErrorRecords.Rows)
{
if (row.RowType == DataControlRowType.DataRow)
{
bool isChecked = row.Cells[0].Controls.OfType().FirstOrDefault().Checked;
for (int i = 1; i < row.Cells.Count; i++)
{
// row.Cells[i].Controls.OfType().FirstOrDefault().Visible = !isChecked;
if (row.Cells[i].Controls.OfType().ToList().Count > 0)
{
row.Cells[i].Controls.OfType().FirstOrDefault().Visible = isChecked;
}
if (row.Cells[i].Controls.OfType().ToList().Count > 0)
{
row.Cells[i].Controls.OfType().FirstOrDefault().Visible = isChecked;
}
if (isChecked && !isUpdateVisible)
{
isUpdateVisible = true;
}

}
}
}
btnUpdate.Visible = isUpdateVisible;
}

protected void Update(object sender, EventArgs e)
{
foreach (GridViewRow row in GVErrorRecords.Rows)
{
if (row.RowType == DataControlRowType.DataRow)
{
bool isChecked = row.Cells[0].Controls.OfType().FirstOrDefault().Checked;
if (isChecked)
{

}
}
}
btnUpdate.Visible = false;
this.BindGrid3();
}