组合框SelectedValue属性不起作用 [英] ComboBox SelectedValue property doesn't work

问题描述

我想添加对象到组合框，并使用的SelectedValue 属性在组合框中选择和项目，但它不工作：的SelectedValue 仍是空的分配之后。

 类ComboBoxItem
        {
            字符串名称;
            对象的值;

            公共字符串名称{{返回名称; }}
            公共对象值{{返回值; }}

            公共ComboBoxItem（字符串名称，对象的值）
            {
                this.name =名称;
                THIS.VALUE =价值;
            }

            公众覆盖布尔等于（obj对象）
            {
                ComboBoxItem项目= OBJ为ComboBoxItem;
                返回项目= NULL和放大器;！＆安培; Value.Equals（item.Value）;
            }
        }

            operatorComboBox.Items.Add（新ComboBoxItem（GLEICH，SearchOperator.OpEquals））;
            operatorComboBox.Items.Add（新ComboBoxItem（Ungleich，SearchOperator.OpNotEquals））;


            operatorComboBox.ValueMember =值;
            //的SelectedValue仍然是该语句之后空
            operatorComboBox.SelectedValue = SearchOperator.OpNotEquals;
 

解决方案

ValueMember 通过数据源绑定时只适用属性，而不是当你与 Items.Add 。试试这个：

  VAR项目=新的名单，其中，ComboBoxItem>（）;
items.Add（新ComboBoxItem（...））;

operatorComboBox.DataSource =项目;
 

顺便说一句，请注意，当您覆盖等于，你也应该覆盖和实施 GetHash code 。

I'm trying to add objects into a combobox and use SelectedValue property to select and item in the combobox but it does not work: SelectedValue is still null after the assignment.

        class ComboBoxItem
        {
            string name;
            object value;

            public string Name { get { return name; } }
            public object Value { get { return value; } }

            public ComboBoxItem(string name, object value)
            {
                this.name = name;
                this.value = value;
            }

            public override bool Equals(object obj)
            {
                ComboBoxItem item = obj as ComboBoxItem;
                return item!=null && Value.Equals(item.Value);
            }
        }          

            operatorComboBox.Items.Add(new ComboBoxItem("Gleich", SearchOperator.OpEquals));
            operatorComboBox.Items.Add(new ComboBoxItem("Ungleich", SearchOperator.OpNotEquals));


            operatorComboBox.ValueMember="Value";
            //SelectedValue is still null after this statement
            operatorComboBox.SelectedValue = SearchOperator.OpNotEquals; 

解决方案

ValueMember is only applicable when databinding via DataSource property, not when you add items manually with Items.Add. Try this:

var items = new List<ComboBoxItem>();
items.Add(new ComboBoxItem(...));

operatorComboBox.DataSource = items;

Btw, note that when you override Equals, you should also override and implement GetHashCode.

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