c# - 如何确定组合框是否包含值成员？

Question

情况是我有 2 个控件，一个文本框和一个组合框。用户可以在组合框中选择一些东西，它用值成员填充文本框，如果用户在文本框中输入，我想检查它是否存在于组合框的值中，然后选择相应的显示成员。

我期待的方法是这样的

if(cmb1.valueMembers.Contains(txt1.Text))

但我找不到这样的东西，我也认为循环通过它们可以找到它？所以我有

foreach (System.Data.DataRowView row in cmb1.Items)
        {}

但在行中的任何地方都找不到值成员？

谢谢

Answer 1

好的，这是一个简单的例子，但我想这是主要思想。我们为 ValueMember 和DisplayMember 提供了一个MyClass。IdName

 public partial class Form1 : Form
{
    class MyClass
    {
        public MyClass(string name, int id)
        {
            Name = name;
            Id = id;
        }
        public string Name { get; set; }
        public int Id { get; set; }
    }

    List<MyClass> dsList = new List<MyClass>();

    public Form1()
    {

        for (int i = 0; i < 10; i++)
        {
            dsList.Add(new MyClass("Name" + i , i));
        }

        InitializeComponent();

        comboBox1.DataSource = dsList;
        comboBox1.ValueMember = "Id";
        comboBox1.DisplayMember = "Name";
    }

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        //Checks if item with the typed Id exists in the DataSource
        // and selects it if it's true
        int typedId = Convert.ToInt32(textBox1.Text);
        bool exist = dsList.Exists(obj => obj.Id == typedId);
        if (exist) comboBox1.SelectedValue = typedId;

    }


    private void comboBox1_SelectedValueChanged(object sender, EventArgs e)
    {
        MyClass obj = comboBox1.SelectedValue as MyClass;
        if (obj != null) textBox1.Text = obj.Id.ToString();
    }
}

如果有不清楚的地方，请随时询问。

PS：在示例中，我假设将在文本框中输入整数

Answer 2

游戏有点晚了，但我找不到任何有用的东西，所以我想出了这个简单的解决方案：

comboBox1.Items.OfType<SomeType>().Any(x => x == YourValue)

或者：

comboBox1.Items.OfType<SomeType>().Any(x => x.SomeProperty == YourValue)

---

演示示例：

class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

// ...

var people = new List<Person>() { /* Add some data */ };
comboBox1.DisplayMember = "Name";
comboBox1.ValueMember = "Id";
comboBox1.DataSource = people;

// ...

bool exists = comboBox1.Items.OfType<Person>().Any(p => p.Id == 1);

或者，如果您需要获取项目的索引，您可以使用以下内容：

var person = comboBox1.Items.OfType<Person>().FirstOrDefault(p => p.Id == 1);
var index = (person != null) ? comboBox1.Items.IndexOf(person) : -1;

Answer 3

ListSubCategoryProduct = await Task.Run<List<SubCategoryProduct>>(() => { 
    return productsController.ListSubCategoryProduct(CategoryProductId); }); // <- I search the database

                CboSubCategory.DataSource = ListSubCategoryProduct;
                CboSubCategory.DisplayMember = "Description";
                CboSubCategory.ValueMember = "SubCategoryProductId";

                CboSubCategory.AutoCompleteMode = AutoCompleteMode.Suggest;
                CboSubCategory.AutoCompleteSource = AutoCompleteSource.ListItems;

                this.CboSubCategory.SelectedValue = 1; // <- SubCategoryProductId. You have to know the ID.

Answer 4

Private Sub ComboBox1_SelectedValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedValueChanged
    If ComboBox1.SelectedIndex = -1 Then              
        Return
    Else
        TextBox1.Text = ComboBox1.SelectedValue.ToString   ' if find then show their displaymember in combobox.
    End If


Private Sub TextBox1_Leave(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.Leave
    Dim value As String = TextBox1.Text
    ComboBox1.SelectedValue = value                                    ' if find then show their displaymember in combobox.

    If ComboBox1.SelectedValue Is Nothing Then                          ' if the id you entered in textbox is not find.
        TextBox1.Text = String.Empty

    End If