delete rows in datagridview in c#

Question

I want to delete some rows from datagridview based on condition in c#,but at run time i find that row,though by debugging  my code is working properly.

 

My code is as follows:-

foreach (DataGridViewRow item in this.dataGridView1.Rows)

{

if ((item.Cells["Start Time"].Value.ToString() != "22:00:00") || (item.Cells["Start Time"].Value.ToString() != "18:00:00"))

{

dataGridView1.Rows.Remove(item);

}

}

 

dataGridView1.Rows.Remove(item);

Instead of this line,I have even tried

 dataGridView1.Rows.RemoveAt(item.Index)

 

i have even tried to delete rows from datatable  and then bind in datagridview ,but nothings helped me.

why my above code fails to delete record in datagridview,PLZ help me out.