Question

我正在为我的学校做一个项目，我必须在那里制作一个C＃Windows Forms应用程序，让我可以与我的PostgreSQL数据库进行交互。我已经创建了一个列表框，它应该从我的数据库中获取表的名称，当我选择这些名称时，该表中的数据将显示在表单中的datagridview对象中。但问题是，我的所有列表框值都是System.Data.DataRowView，而datagridview只显示列表中第一个表的值。

代码：

    DataTable tabulusaraksts = new DataTable();
    DataTable tabula = new DataTable();
    NpgsqlDataAdapter adapter = new NpgsqlDataAdapter();
    NpgsqlDataAdapter adapter2 = new NpgsqlDataAdapter();
    string tab;
    public datubaze()
    {
        InitializeComponent();
        string connectionstring = "Server=localhost;Port=5432;UserId=postgres;Password=students;Database=retrospeles;";
        //string connectionstring = String.Format("Server={0};Port={1};" +
        //       "User Id={2};Password={3};Database={4};",
        //        serveris.ToString(), port.ToString(), user.ToString(),
        //        password.ToString(), database.ToString());
        NpgsqlConnection ncon = new NpgsqlConnection(connectionstring);
        NpgsqlCommand listfill = new NpgsqlCommand("select table_name from INFORMATION_SCHEMA.tables WHERE table_schema = ANY (current_schemas(false));", ncon);
        adapter.SelectCommand = listfill;
        adapter.Fill(tabulusaraksts);
        listBox1.DataSource = tabulusaraksts;
        listBox1.DisplayMember = "table_name";
        NpgsqlCommand showtable = new NpgsqlCommand("select * from " + tab +";" , ncon);
        adapter2.SelectCommand = showtable;
    }
public void listBox1_SelectedIndexChanged(object sender, EventArgs e)
    {

        tab = listBox1.GetItemText(listBox1.SelectedItem);
        adapter2.Fill(tabula);
        dataGridView1.DataSource = tabula;
}

Answer 1

该代码应该有效。我尝试了一些测试数据，ListBox填充了正确的值。当然，请尝试将ValueMember设置为

listBox1.DisplayMember = "table_name";

我认为最好的方法是使用循环或Linq列表向DataTable添加ListBox行。填写tabulusaraksts后，DataRows进行迭代并将其作为项目添加到ListBox，而不设置DataSource这样的内容（Linq）：

adapter.SelectCommand = listfill;
adapter.Fill(tabulusaraksts);
listBox1.Items.AddRange(tabulusaraksts.AsEnumerable().Select(row => row[0].ToString()).ToArray());
NpgsqlCommand showtable = new NpgsqlCommand("select * from " + tab +";" , ncon);
adapter2.SelectCommand = showtable;

或使用foreach循环

adapter.SelectCommand = listfill;
adapter.Fill(tabulusaraksts);

listBox1.Items.Clear();
foreach (DataRow row in tabulusaraksts.Rows)
{
    listBox1.Items.add(tabulusaraksts[0].ToString());
}

NpgsqlCommand showtable = new NpgsqlCommand("select * from " + tab +";" , ncon);
adapter2.SelectCommand = showtable;

Listbox返回System.Data.DataRowView而不是值

1 个答案: