图表以从 textbox.text 中获取用户的值并在 y 轴上绘制最大值和最小值以 hh:mm 为单位

Question

Here is the screen shot..I did what you said but now when I run the code ...the x-axis scale just goes blank ...

chart1.ChartAreas[0].AxisX.Minimum = Convert.ToDateTime(textBox7.Text).ToOADate();
chart1.ChartAreas[0].AxisX.Maximum = Convert.ToDateTime(textBox8.Text).ToOADate(); 

and here is the screen shot in dubugging mode, it shows some random numbers... Don't know whats that...

It's the same even if i do this:

chart1.ChartAreas[0].AxisX.Minimum = DateTime.Parse(textBox7.Text).ToOADate();
chart1.ChartAreas[0].AxisX.Maximum = DateTime.Parse(textBox8.Text).ToOADate(); 

previous values are as shown in the fig below..

these are the values from DataGridView I am displaying on chart for Time vs Temperature...and the red circle indicates the Time values, whose Min and Max values is what I want to trying to take from Textbox7.text and Textbox8.text and display on chart X-AXIS....

Answer 1

By default, Minimum and Maximum are waiting for doubles, and that's what you're doing here:

chart1.ChartAreas[0].AxisX.Minimum = Convert.ToDouble(textBox1.Text);

But you're trying to convert 09:27 to a double which can't be done because it's in an invalid format.

But if you want to work with time, you have to set XValueType to Time and parse your TextBox to a DateTime like so:

chart1.ChartAreas[0].AxisX.Minimum = DateTime.Parse(textBox1.Text).ToOADate();

And it should do the trick.

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Using DateTime.Parse(textBox1.Text) will create an object with today's date and the requested Time. In your case, you're interested in keeping the date ( 08/30/2016 ). What you have to do is:

// Get the old date
DateTime currentDateMin = DateTime.FromOADate(chart1.ChartAreas[0].AxisX.Minimum);
// Parse the date you want to set
DateTime requestesd = DateTime.Parse(textBox1.Text);
// Set the time part
DateTime newDateMin = new DateTime(currentDateMin.Year, currentDateMin.Month, currentDateMin.Day, requestesd.Hour, requestesd.Minute, requestesd.Second);
// Assign to your axis
chart1.ChartAreas[0].AxisX.Minimum = newDateTime.ToOADate();