将DataGridView绑定到实体的“主从细节"中.方式 [英] Bind DataGridView to Entities in a "master-detail" manner

问题描述

我正在尝试在两个DataGridView之间建立主从关系.我有一个EntityModel，其中两个实体通过"ClientComissions"关联连接.它们是从现有数据库生成的，并且具有导航属性，可以很好地工作.证明(使用提到的EntityModel的控制台应用程序):

I'm trying to establish a master-detail relation between two DataGridView. I have an EntityModel with two entities connected by "ClientComissions" Association. They were generated from an existing DB, and have Navigation Properties, that work well. Proof (console app using mentioned EntityModel):

            using (var context = new MnxEntities())
        {
            Client client = context.Clients.FirstOrDefault();
            // profiler: "SELECT TOP (1) ... FROM [Clients] AS [c]" - Ok!
            Console.WriteLine("Client: {0}", client.Name);
                foreach (Comission comission in client.NavComissions)
                // profiler: "SELECT ... FROM [Comissions] WHERE [StateCode] = '20971504'" - Ok!
                {
                    Console.WriteLine("Agreement number: {0}", comission.Dog_Num);
                }
        }

---

但是我无法在Windows窗体上以主从方式绑定两个DataGridView:

---

But I can't bind two DataGridViews in a master-detail manner on windows form:

        private void tabComissions_Enter(object sender, EventArgs e)
    {
        using (var context = new MnxEntities())
        {
            clientDataGridView.DataSource  = context.Clients;

            comissionsDataGridView.DataSource = clientDataGridView.DataSource;
            comissionsDataGridView.DataMember = "WHAT SHOULD BE HERE?";
        }
    }

---

我知道有一个BindingContext，它必须使用CurrencyManager完成所有工作，而无需手写代码.

---

I know there is a BindingContext, that must do all the job using CurrencyManager, with no hand-written code needed.

我在这里停留了很多时间.请帮助.

I've stuck here for to much time. Help please.

UPD:

        private void AnswerFromStackRefactored()
    {
        using (var context = new MnxEntities())
        {
            clientBindingSource.DataSource = context;
            clientBindingSource.DataMember = "Clients";

            navComissionsBindingSource.DataSource = clientBindingSource;
            navComissionsBindingSource.DataMember = "NavComissions";
        }

    }

此代码仅对网格中的第一个客户端加载一次佣金.但是，当我更改客户网格"中的当前行"时，不再需要查询数据库，并且navComissionsGrid始终显示第一个客户的佣金.:(

this code loads Comissions only once, for the first client in grid. But when I change Current row in Clients Grid there is no more query to DB and navComissionsGrid always show comission for the first client. :(

推荐答案

在窗体上拉两个ListView，并将它们分别命名为lstcategory和lstProduct.然后复制下面的代码(非常简单).您可以将相同的概念应用于您的问题.

Pull two ListViews on a Form and name them as lstcategory and lstProduct respectively. Then copy the code below [its very simple]. You may apply the same concept to your problem.

public partial class MasterDetail : Form
    {
        public MasterDetail()
        {
            InitializeComponent();
        }

        private BindingManagerBase categoryBinding;
        private DataSet ds;

        private void MasterDetail_Load(object sender, EventArgs e)
        {
            ds = GetCategoriesAndProducts();

            // Bind the lists to different tables.
            lstCategory.DataSource = ds.Tables["Categories"];
            lstCategory.DisplayMember = "CategoryName";

            lstProduct.DataSource = ds.Tables["Products"];
            lstProduct.DisplayMember = "ProductName";

            // Track the binding context and handle position changing.
            categoryBinding = this.BindingContext[ds.Tables["Categories"]];
            categoryBinding.PositionChanged += new EventHandler(Binding_PositionChanged);

            // Update child table at startup.
            UpdateProducts();
        }

        private void Binding_PositionChanged(object sender, System.EventArgs e)
        {
            UpdateProducts();
        }

        private void UpdateProducts()
        {
            string filter;
            DataRow selectedRow;

            // Find the current category row.
            selectedRow = ds.Tables["Categories"].Rows[categoryBinding.Position];

            // Create a filter expression using its CategoryID.
            filter = "CategoryID='" + selectedRow["CategoryID"].ToString() + "'";

            // Modify the view onto the product table.
            ds.Tables["Products"].DefaultView.RowFilter = filter;
        }

        public DataSet GetCategoriesAndProducts()
        {
            DataTable category = new DataTable("Categories");
            category.Columns.Add("CategoryID");
            category.Columns.Add("CategoryName");

            category.Rows.Add(new object[] { "1", "Food" });
            category.Rows.Add(new object[] { "2", "Beverage" });


            DataTable product = new DataTable("Products");
            product.Columns.Add("CategoryID");
            product.Columns.Add("ProductName");

            product.Rows.Add(new object[] { "1", "Rice" });
            product.Rows.Add(new object[] { "1", "Pasta" });

            product.Rows.Add(new object[] { "2", "Cola" });
            product.Rows.Add(new object[] { "2", "Coffee" });
            product.Rows.Add(new object[] { "2", "Tea" });


            DataSet ds = new DataSet();
            ds.Tables.Add(category);
            ds.Tables.Add(product);

            // Set up a relation between these tables (optional).
            DataRelation relCategoryProduct = new DataRelation("CategoryProduct",
              ds.Tables["Categories"].Columns["CategoryID"],
              ds.Tables["Products"].Columns["CategoryID"]);

            ds.Relations.Add(relCategoryProduct);

            return ds;
        }

    }       

这篇关于将DataGridView绑定到实体的“主从细节"中.方式的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！