How can I subtract?

Question

I want the result of :

count220 - countTotal = ?

sum220 - sumTotal = ?

 

Here is my code:

 

var countTotal = Convert.ToInt32(count1 + count2 + count3 );

double sumTotal = Convert.ToDouble(sum1 + sum2 + sum3 );

var count220 = 0;

foreach (DataGridViewRow g1 in dataGridView1.Rows)

{

if (g1.Cells[2].Value.ToString() != "")

count220 = count220 + Convert.ToInt32(g1.Cells[5].Value);

}

double sum220 = 0;

foreach (DataGridViewRow g1 in dataGridView1.Rows)

{

if (g1.Cells[2].Value.ToString() != "")

sum220 = sum220 + Convert.ToDouble(g1.Cells[5].Value);

}