用户输入多项式函数

Question

我需要创建一个应用程序，用户可以在其中输入不同的多项式函数。首先，用户必须选择特定等级的多项式函数（在0和10之间）。在所选等级的基础上，应该出现不同数量的文本框，用户可以在其中指定系数的值。例如，用户选择等级“4” - >出现5个文本框。它应该如下所示：

___我___ a2 ___ a1 ___ a0 ___

___：代表单个文本框

在使用ItemsControl时，我也在努力水平对齐文本框。我还想将用户输入的值保存在ViewModel中。我已经尝试了很多东西，但我无法弄明白该怎么做。到目前为止这是我的代码：

<ItemsControl ItemsSource="{Binding SelectedGrade}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBox Height="20" Width="100"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

public ObservableCollection<double> SelectedGrade
    {
        get
        {
            ObservableCollection<double> newCol = new ObservableCollection<double>();
            for (int i = 0; i < this.SelectedNum + 1; i++)
            {
                newCol.Add(0);
            }

            this.selectedGrade = newCol;
            return newCol;
        }
        set
        {
            //...
        }
    }


public ICommand AddPolyFuncCommand
    {
        get
        {
            return new Command(obj =>
            {
                Function newPolyFunc = new PolyFunction(this.Coefficients);
                Functions.Add(newPolyFunc);
                CalculatePoints();
            });
        }
    }

Answer 1

根据评论，我将提供一个小例子如何做（我添加了1-2个额外的，这可能是方便的）

使用Text="{Binding Value}"绑定到VM中的Value

使用Wrappanel水平显示它

（可选）使用AlternationIndex标记系数

（可选）更改FlowDirection以显示它，就像您勾画它一样

<!-- Combobox to select from the available Grades and store the selected in the SelectedGrade -->
<ComboBox ItemsSource="{Binding AvailableGrades}" SelectedValue="{Binding SelectedGrade}" VerticalAlignment="Top" HorizontalAlignment="Left"/>

<!-- Use Alternationcount to label the coefficients properly and Flowdirection to keep a0 on the right side -->
<ItemsControl ItemsSource="{Binding Coefficients}" AlternationCount="11" FlowDirection="RightToLeft">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                <!-- Textbox to enter Coefficient (eg. a0 would be SelectedGrade[0] in code)-->
                <TextBox Text="{Binding Value}" Width="50" VerticalAlignment="Center"/>
                <!-- Labeling of the Coefficient using the AlternationIndex and a String Format -->
                <Label Content="{Binding Path=(ItemsControl.AlternationIndex), RelativeSource={RelativeSource TemplatedParent}}" ContentStringFormat="a{0}"/>
            </StackPanel>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
    <!--  Use a WrapPanel as ItemsPanel to align the Entries horizontally -->
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <WrapPanel/>
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
</ItemsControl>

看起来像这样（没有成绩文本框，只有右侧的东西）

---

编辑

要正确调整系数的数量，需要一点点逻辑，但首先 - >适当地重命名属性并定义它们的可能值（这有助于为属性创建适当的逻辑）

AvailableGrades = 0,1,2 ... 10

SelectedGrade∈{0,1,2 ... 10}

系数= a（0），a（1）... a（SelectedGrade）

//Unfortunately it is not possible to use a Value Type and bind to it due it has no Getter/Setter therefore we need a little wrapper
public class ValueTypeAsClass<T>
{
    public T Value { get; set; }
    public static implicit operator ValueTypeAsClass<T>(T v)
    {
        return new ValueTypeAsClass<T> { Value = v };
    }
    public static implicit operator T(ValueTypeAsClass<T> v)
    {
        return v.Value;
    }
}

//member variable for select grade
private int _selectedGrade = 0;
//List of Coefficients (renamed from SelectedGrade)
public ObservableCollection<ValueTypeAsClass<double>> Coefficients { get; set; } = new ObservableCollection<ValueTypeAsClass<double>>() { 0d };
//Available (valid) Grades to select from in the ComboBox
public List<int> AvailableGrades { get; private set; } = Enumerable.Range(0, 11).ToList();
//Currently selected grad with logic to adjust the coefficient amount
public int SelectedGrade
{
    get { return _selectedGrade; }
    set
    {
        _selectedGrade = value;
        //Clear Coefficients and add the necessary amount
        Coefficients.Clear();
        for (int i = 0; i <= _selectedGrade; i++) { Coefficients.Add(0); }
    }
}