Question

使用linq运行一个项目到sql模型，并将我的组合绑定到bindingsource控件，我有两个组合框，首先显示一个表显示数据库表名（ID，TableName），第二个应该绑定到选定的表中第一个组合，我尝试了这段代码：

        private void ComboBox1_TextChanged(object sender, EventArgs e)
    {
        if (ComboBox1.Text == "Customers")
        {
            var qry = (from u in dc.Customers
                       select u).ToList();
            comboBox2.ValueMember = "CustomerID";
            comboBox2.DisplayMember = "CompanyName";
            comboBox2.DataSource = qry;
        }
        if (ComboBox1.Text == "Suppliers")
        {
            var qry = (from u in dc.Suppliers
                       select u).ToList();
            comboBox2.ValueMember = "SupplierID";
            comboBox2.DisplayMember = "CompanyName";
            comboBox2.DataSource = qry;
        }
    }

使用上面的代码我可以显示第一个组合项目，默认情况下我也可以显示第二个组合项目，但是当我更改第一个组合内容时，我在comboBox2.ValueMember =“SupplierID”中得到错误; ：System.ArgumentException未处理 Message =无法链接到新的Value成员。请问如何将combobox2.ValueMember重置为新的字段名称？

Answer 1

您只需要返回ValueMember＆amp;的列。 DisplayMember

var qry = (from u in dc.Suppliers
            select new { a.SupplierID, a.CompanyName}).ToList();
            comboBox2.ValueMember = "SupplierID";
            comboBox2.DisplayMember = "CompanyName";
            comboBox2.DataSource = qry;

Answer 2

必须在更改其ValueMember之前初始化组合框属性，如下所示：

        **comboBox2.DataSource = null;**
        if (ComboBox1.Text == "Customers")
        {
            var qry = (from u in dc.Customers
                       select new { u.CustomerID, u.CompanyName }).ToList();
            comboBox2.ValueMember = "CustomerID";
            comboBox2.DisplayMember = "CompanyName";
            comboBox2.DataSource = qry;
        }
        if (ComboBox1.Text == "Suppliers")
        {
            var qry = (from u in dc.Suppliers
                       select new { u.SupplierID, u.CompanyName }).ToList();
            comboBox2.ValueMember = "SupplierID";
            comboBox2.DisplayMember = "CompanyName";
            comboBox2.DataSource = qry;
        }

如何在其他组合框值变化时动态更改组合框

2 个答案: