C＃的WinForms - 过滤1组合框基于另一个组合框的数据绑定datagridview的价值 [英] C# WinForms - filtering one combobox based on the value of another combobox in a databound datagridview

问题描述

我有4个表 - 代理，客户，县，乡。代理商和客户都有一个镇场和县现场。我对每个表一个DataGridView。这些都是伟大的工作。我有城区和县利用城镇和县表作为数据源组合框。

I have 4 tables - Agents, Customers, Counties and Towns. Agents and Customers both have a Town field and a County field. I have a DataGridView for each table. These are working great. I have the Town and County as comboboxes using the Towns and Counties table as the datasource.

的问题是，它不过滤的基础上选定的县镇。我想它要做到这一点，但没有选项来筛选基于另一个字段的值的组合框字段。

The problem is that it does not filter the Town based on the selected County. I would like it to do this, but there is no option to filter a combobox field based on the value of another field.

我已搜查这个了一段时间，但无法找到什么有用的东西。

I have searched this up for a while but cant find anything useful.

谁能说服我通过如何做到这一点，好吗？

Can anyone talk me through how to do this, please?

在此先感谢

问候，

理查德

PS我使用Visual Studio 2010和大多设计视图。

PS I am using Visual Studio 2010 and mostly design view.

推荐答案

您可以使用数据视图 为您的组合框的数据源，因为这可以让你基于一个标准来过滤行（通过 的RowFilter 属性）。我将展示一个简单的例子，涉及用于选择一个国家，在该国镇两级组合框。

You can use DataView as a data source for your comboboxes, since this allows you to filter rows based on a criterion (via the RowFilter property). I'll show a simple example involving two comboboxes used for selecting a country and a town in that country.

首先，设置一些数据要使用：

First, set up some data to be used:

// set up DataTable with countries:
countriesTable = new DataTable("Countries");
countriesTable.Columns.Add("CountryID", typeof(int));
countriesTable.Columns.Add("CountryName", typeof(string));
countriesTable.Rows.Add(1, "England");
countriesTable.Rows.Add(2, "Spain");
...

// set up DataTable with towns:
townsTable = new DataTable("Towns");
townsTable.Columns.Add("TownID", typeof(int));
townsTable.Columns.Add("TownName", typeof(string));
townsTable.Columns.Add("CountryID", typeof(int));   // <-- this is a foreign key
townsTable.Rows.Add(1, "London", 1);
townsTable.Rows.Add(2, "Brighton", 1);
townsTable.Rows.Add(3, "Barcelona", 2);
...

---

接下来，数据-bind的组合框的数据：

---

Next, data-bind the comboboxes to the data:

// bind countries to country combobox:
countryComboBox.DataSource = null;
countryComboBox.DisplayMember = "CountryName";
countryComboBox.ValueMember = "CountryID";
countryComboBox.DataSource = countriesTable;

// bind towns to town combobox:    
townsView = new DataView(townsTable, "CountryID = 1", ...);  // use foreign key
townComboBox.DataSource = null;                              // in a row filter
townComboBox.DisplayMember = "TownName";
townComboBox.ValueMember = "TownID";
townComboBox.DataSource = townsView;

---

最后，当其他国家在该国选择组合框，更新行过滤器：

---

Finally, whenever another country is selected in the country combobox, update the row filter:

private void countryComboBox_SelectedIndexChanged(object sender, EventArgs e)
{
    ...
    townsView.RowFilter = string.Format("CountryID = {0}",
                                            countryComboBox.SelectedValue);
}

我相信你可以使用数据绑定和一个自定义自动最后一步格式事件处理程序，但我不会赘述了。

I believe you could automate this last step using databinding and a custom Format event handler, but I won't go into details.

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