WinForm C#，根据两个条件填充组合框

Question

我需要根据所选城市和所选类型名称填充组合框1。

我用以下内容填充城市组合框：

        private void FillCityTable()
    {
        dtCity.Columns.Add("CityID", typeof(int));//ID will be a number
        dtCity.Columns.Add("CName");//defaults typof is string

        dtCity.Rows.Add(1, "Regina");
        dtCity.Rows.Add(2, "Saskatoon");
        dtCity.Rows.Add(3, "Winnipeg");
    }
        private void Form1_Load(object sender, EventArgs e)
    {
        FillCityTable();
        FillTypeTable();
        FillData();

        cboCity.DataSource = dtCity;
        cboCity.DisplayMember = "CName";
    }

我根据所选城市填充“类型”组合框

        private void FillTypeTable()
    {
        dtType.Columns.Add("CityID", typeof(int));//ID will be a number
        dtType.Columns.Add("TypeName");//defaults typof is string

        dtType.Rows.Add(1, "H1");
        dtType.Rows.Add(1, "H2");
        dtType.Rows.Add(1, "H3");
        dtType.Rows.Add(2, "H2");
        dtType.Rows.Add(2, "H1");
        dtType.Rows.Add(2, "H3");
        dtType.Rows.Add(3, "H2");
    }
        private void cboCity_SelectedIndexChanged(object sender, EventArgs e)
    {
        dtSpecificType = dtType.Select("CityID =" + dtCity.Rows[cboCity.SelectedIndex]["CityID"]).CopyToDataTable();
        cboType.DataSource = dtSpecificType;
        cboType.DisplayMember = "TypeName";
    }

主要数据表来自csv文件。 我需要根据所选城市和所选类型名称使用用户名填充组合框1。 到目前为止，我只能根据所选城市填充用户名。我怎样才能得到第二个标准？

        private void cboType_SelectedIndexChanged(object sender, EventArgs e)
    {
        dtSpecificUserNames = dtUserName.Select("CityID =" + dtSpecificType.Rows[cboType.SelectedIndex]["CityID"]).CopyToDataTable();
        combobox1.DataSource = dtSpecificUserNames;
        combobox1.DisplayMember = "Username";
    }

CSV：

CityID,TypeName,Username,Password,MachineID,Picture_File
1,H1,User1,password1,MachineID 1,Airplane
1,H1,User3,password3,MachineID 3,Bread
1,H1,User8,password8,MachineID 8,Boat
1,H2,User11,password11,MachineID 11,Boat
1,H3,User2,password2,MachineID 2,Boat
1,H3,User10,password10,MachineID 10,Airplane
2,H1,User6,password6,MachineID 6,Bread
2,H2,User4,password4,MachineID 4,Airplane
2,H2,User7,password7,MachineID 7,Airplane
2,H3,User5,password5,MachineID 5,Boat
3,H2,User9,password9,MachineID 9,Bread

需要类型标准以及城市标准。

Answer 1

制作

DataTable

的副本，将其指定为 cboType 的

DataSource

，然后在副本上设置

DefaultView.RowFilter

。例如：

public static void TestComboBox() {

    DataTable table = GetDataTable();
    ComboBox combo1 = new ComboBox();
    ComboBox combo2 = new ComboBox();
    ComboBox combo3 = new ComboBox();

    combo1.DisplayMember = "CityId";
    combo1.ValueMember = "CityId";
    combo1.DataSource = table;

    combo2.DisplayMember = "TypeName";
    combo2.ValueMember = "TypeName";
    combo2.DataSource = table;

    DataTable table2 = table.DefaultView.ToTable(); // make a copy

    combo3.DisplayMember = "Username";
    combo3.DataSource = table2;

    EventHandler evt = (o, e) => {
        String cityId = (String) combo1.SelectedValue;
        String typeName = (String) combo2.SelectedValue;
        table2.DefaultView.RowFilter = String.Format("CityId = '{0}' and TypeName = '{1}'", cityId, typeName);
    };

    combo1.SelectedValueChanged += evt;
    combo2.SelectedValueChanged += evt;

    FlowLayoutPanel panel = new FlowLayoutPanel();
    panel.Controls.AddRange(new [] { combo1, combo2, combo3 });
    panel.Dock = DockStyle.Fill;
    Form f = new Form();
    f.Controls.Add(panel);
    Application.Run(f);
}


public static DataTable GetDataTable() {
String data  =
@"CityID,TypeName,Username,Password,MachineID,Picture_File
1,H1,User1,password1,MachineID 1,Airplane
1,H1,User3,password3,MachineID 3,Bread
1,H1,User8,password8,MachineID 8,Boat
1,H2,User11,password11,MachineID 11,Boat
1,H3,User2,password2,MachineID 2,Boat
1,H3,User10,password10,MachineID 10,Airplane
2,H1,User6,password6,MachineID 6,Bread
2,H2,User4,password4,MachineID 4,Airplane
2,H2,User7,password7,MachineID 7,Airplane
2,H3,User5,password5,MachineID 5,Boat
3,H2,User9,password9,MachineID 9,Bread";

String[] lines = data.SplitAndTrim('\r', '\n');
String[] header = lines[0].SplitAndTrim(',');

DataTable table = new DataTable();
for (int i = 0; i < header.Length; i++)
    table.Columns.Add(header[i]);

for (int i = 1; i < lines.Length; i++) {
    table.Rows.Add(lines[i].SplitAndTrim(','));
}
return table;
}