为什么KeyDown事件不能与datagridview c＃一起使用？

Question

I am new to c# and using windows forms.

I was looking for an event to use with datagridview when arrow down key in the keyboard is pressed and I found keyDown datagridview event.

What I am trying to do is:

let's say I have datagridview with 4 rows , now when I press arrow down (in the keyboard) I want the highlight (selection) go down and on same time when a row is selected I want the event to check if the row font color is red or not so I used the following code:

 private void dataGridView1_KeyDown(object sender, KeyEventArgs e)
 {

        int RowIndex = dataGridView1.SelectedRows[0].Index;


        if (dataGridView1.Rows[RowIndex].DefaultCellStyle.ForeColor == Color.Red)
        {
            MessageBox.Show("This row font is red");
        }               


 }

When I tried this code it does not work well, the problem is:

Say:

Row0 font color = black

Row1 font color = red

Row2 font color = black

Row3 font color = black

Now the selected row is Row0 , press arrow down it goes to Row1 but the event doesn't get fired. Now the selected row is Row1 and when I press arrow down the event works but too late, I mean it should get fired when Row1 is selected.

Anyone knows how can I fix it (or any other ideas)? I just want to check rows font color when I press arrow key down in keyboard? Thank you

Answer 1

The KeyDown event fires before the selection actually has changed.

Key events occur in the following order:

 KeyDown KeyPress KeyUp 

So a simple solution is to move your code to the KeyUp event, which happens after the new row selection has happened.

Answer 2

to achieve this you can use event first set the row selection mode with following line

dataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;

then here is the selection changed event mechanism

private void dataGridView1_SelectionChanged(object sender, EventArgs e)
    {
        if (dataGridView1.SelectedRows.Count > 0)
        {
            int RowIndex = dataGridView1.SelectedRows[0].Index;
            if (dataGridView1.Rows[RowIndex].DefaultCellStyle.ForeColor == Color.Black)
            {
                MessageBox.Show("This row font is Black");
            }      
        }
    }