使用C＃在文本框的foreach或while循环中显示行来遍历MySql数据库

Question

I'm having a little trouble with my application, I have a Database connected and have already displays the values from the first row in the database, however I need to have the database iterate through each row and display them accordingly replacing what was previously there and ideally being delayed by a timer

I thought this was the correct way of going about it however it doesn't seem right as now it doesn't display anything and gives me a System.NullReferenceException. I have tried to solve the issue but seems to be having no luck. If you could recommend something to read, that would be greatly helpful just can't see a lot on the internet for my specific problem

Any help will be great first time posting on here so sorry if things are in the wrong format.

    private void FillInTextFields(DataTable table, int ind)
    {
        foreach(DataRow dr in table.Rows)
        {
            foreach(var item in dataRow.ItemArray)
            {
                dataRow = table.Rows[ind];
                txtNHSNumber.Text = dataRow.ItemArray.GetValue(0).ToString();
                txtFirstName.Text = dataRow.ItemArray.GetValue(1).ToString();
                txtLastName.Text = dataRow.ItemArray.GetValue(2).ToString();
                txtTimeDate.Text = dataRow.ItemArray.GetValue(3).ToString();
                txtHeartRate.Text = dataRow.ItemArray.GetValue(4).ToString();
                txtTemp.Text = dataRow.ItemArray.GetValue(5).ToString();
                txtReps.Text = dataRow.ItemArray.GetValue(6).ToString();
                txtDia.Text = dataRow.ItemArray.GetValue(7).ToString();
                txtSys.Text = dataRow.ItemArray.GetValue(8).ToString();
            }
        }
    }

Answer 1

foreach(var item in dataRow.ItemArray)

should be:

foreach(var item in dr.ItemArray)

can put a sleep at the end of the loop to delay before going back to the top.

Answer 2

It seems you have a few issues. First, your inner loop doesn't seem to be necessary. Second, the outer loop is going through all the rows, even though you're specifically passing the row index into your method. Finally, it seems you're using your "dataRow" variable before it's assigned, although I'd have to see more code to be sure. Consider this:

private void FillInTextFields(DataTable table, int ind)
{
    dataRow = table.Rows[ind];
    txtNHSNumber.Text = dataRow.ItemArray.GetValue(0).ToString();
    txtFirstName.Text = dataRow.ItemArray.GetValue(1).ToString();
    txtLastName.Text = dataRow.ItemArray.GetValue(2).ToString();
    txtTimeDate.Text = dataRow.ItemArray.GetValue(3).ToString();
    txtHeartRate.Text = dataRow.ItemArray.GetValue(4).ToString();
    txtTemp.Text = dataRow.ItemArray.GetValue(5).ToString();
    txtReps.Text = dataRow.ItemArray.GetValue(6).ToString();
    txtDia.Text = dataRow.ItemArray.GetValue(7).ToString();
    txtSys.Text = dataRow.ItemArray.GetValue(8).ToString();
}

You'll just need to call this method with the particular index you want to display.

You can also remove the ItemArray.GetValue stuff, and just go with this:

private void FillInTextFields(DataTable table, int ind)
{
    dataRow = table.Rows[ind];
    txtNHSNumber.Text = dataRow[0].ToString();
    txtFirstName.Text = dataRow[1].ToString();
    txtLastName.Text = dataRow[2].ToString();
    txtTimeDate.Text = dataRow[3].ToString();
    txtHeartRate.Text = dataRow[4].ToString();
    txtTemp.Text = dataRow[5].ToString();
    txtReps.Text = dataRow[6].ToString();
    txtDia.Text = dataRow[7].ToString();
    txtSys.Text = dataRow[8].ToString();
}

Answer 3

Not sure why you are passing int ind in this method it's not needed.

private void FillInTextFields(DataTable table)
{
    txtNHSNumber.Text = table.Rows[0].ItemArray[0];
    txtFirstName.Text = table.Rows[0].ItemArray[1];
    txtLastName.Text = table.Rows[0].ItemArray[2];
    txtTimeDate.Text = table.Rows[0].ItemArray[3];
    txtHeartRate.Text = table.Rows[0].ItemArray[4];
    txtTemp.Text = table.Rows[0].ItemArray[5];
    txtReps.Text = table.Rows[0].ItemArray[6];
    txtDia.Text = table.Rows[0].ItemArray[7];
    txtSys.Text = table.Rows[0].ItemArray[8];
}