如何在datagridview中更改行的颜色C＃

Question

I have this part of code, but not working..

       foreach (DataGridViewRow row in dg1.Rows)
        {
            var now = DateTime.Now.Day;
            var expirationDate = DateTime.Parse(row.Cells[2].Value.ToString()).Day;

            if (now == expirationDate)
            {
                row.DefaultCellStyle.BackColor = Color.Red; 
            }
        }

Answer 1

Not good idea to compare classes/structs like that(with == operator)

try using

if(DateTime.Compare(now, expirationDate) == 0)

Answer 2

Your problem is not the comparison you're performing (as others are referring), but it would be better to compare Date using DateTime.Compare method.

The problem is you're not checking for NewRow . It causes exception when you try to read an empty Row .

foreach (DataGridViewRow row in dg1.Rows)
{
    if (!row.IsNewRow)
    {
        //your code
    }
}

Answer 3

Have you tried replacing foreach with for ?

for (int i = 0; i < dg1.Rows.Length; i++)
    {
        var now = DateTime.Now.Day;
        var expirationDate = DateTime.Parse(dg1.Rows[i].Cells[2].Value.ToString()).Day;

        if (now == expirationDate)
        {
            dg1.Rows[i].DefaultCellStyle.BackColor = Color.Red; 
        }
    }

The collection used in foreach is immutable.