我得到了这个异常：System.FormatException：'输入字符串的格式不正确。'

Question

I want to make a management program with an SQL database attached. My problem is that I want to gather all the values from one column to a textbox. That column [7] from the datagridview has values based on the calculation of 2 other columns [4]and [5] in the same datagridview formated as money.

I tried to convert it to string or int without success. Please Help!

    public void gridTotal()
    {
        double sum = 0;
        for (int i = 0; i < dataGridView1.Rows.Count; ++i)
        {
            sum += Convert.ToDouble(dataGridView1.Rows[i].Cells[7].Value);
        }
        facturaTotal.Text = sum.ToString("C");
    }

Answer 1

dataGridView1.Rows[i].Cells[7].Value

may be null or empty String or something else, which cannot be converted into double. Instead I would recommend

double val = 0;
if (double.TryParse(dataGridView1.Rows[i].Cells[7].Value, out val)) sum += val;

Answer 2

If the cells contain real numbers written with a dot, like 2.3 , this error will occur. It is common mistake, you should use CultureInfo to avoid this problem.

sum += Double.Parse(dataGridView1.Rows[i].Cells[7].Value, CultureInfo.InvariantCulture);