如何从 c# 中的组合框获取浮动值

Question

Please help me in this situation

float sumofgradeintocradit = float.Parse(comboBox1.Text);

But an exception caught say "Input string was not in a correct format."

What is the problem please give me some solution I want to take an value from a combo box and store as an float.

Answer 1

Instead of trying to convert display text back into a float, you can use a custom object, which allows holding values separate from the shown text.

Example:

private class ComboItem
{
    public string ItemText  { get; set; }
    public float  ItemFloat { get; set; }

    public ComboItem(string itemText, float itemFloat)
    {
        this.ItemText  = itemText;
        this.ItemFloat = itemFloat;
    }

    public override string ToString()
    {
        return this.ItemText;
    }
}

private void AddItemsToComboBox
{
    comboBox1.Items.Add(new ComboItem("One Point Two", 1.2f));
    comboBox1.Items.Add(new ComboItem("Three Point Four", 3.4f));
}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    var selectedFloat = ((ComboItem)comboBox1.SelectedItem).ItemFloat;
    Debug.Print("Selected: " + selectedFloat);
}

This also works for other things like the ListView.

Answer 2

comboBox1.Text does not contain a flot in the right format.

For debugging Print / trace the value to confirm it.

You can add a client side validation to make sure it is in the right format.

After that if it is a client server app you can add a server side validation to handle the exceptions mentioned in the following MSDN and reprompt the user for input by using try parse or try catch. http://msdn.microsoft.com/en-us/library/2thct5cb(v=vs.110).aspx

Reference: Also see the following on parsing numeric stringshttp://msdn.microsoft.com/en-us/library/xbtzcc4w(v=vs.110).aspx

Answer 3

If I were you I would try this:

float sumofgradeintocradit ;
if (float.TryParse(comboBox1.Text, out _))
    sumofgradeintocradit = float.Parse(comboBox1.Text);

This checks to see if the combobox1.text is a valid float, and if so, it assigns the value to sumofgradeintocradit

HTH