C# Invalid expression term '+='

for(int i=0; i <= dataGridView1.Rows.Count; i++)
        {
            string point_value += dataGridView1.Rows[i].Cells[1].Value + "|"; 
        }

Does anyone know why I am getting error (Invalid expression term ‘+=’ for the above code?

>Solution :

you create new variable with in your for loop that the reason

if you need to store data each loop you should create variable outside loop

like this

string point_value;
for(int i=0; i <= dataGridView1.Rows.Count; i++)
    {
        point_value += dataGridView1.Rows[i].Cells[1].Value + "|"; 
    }

for more information about loop pattern here