想开发一个，能根据所选择的数据库名称，来统计该数据内各表的行数有多少的小窗体；

想开发一个，能根据所选择的数据库名称，来统计该数据内各表的行数有多少的小窗体，如下图那样；代码如下，之前数据库名称都是文本框，但改为下拉菜单后，就不知怎么写了，请指导一下，谢谢

```c#
 private void button1_Click(object sender, EventArgs e)
        {
            String connectionString = String.Format("server={0};uid={1};pwd={2};", textBoxHost.Text, textBoxUser.Text, textBoxPassword.Text);
            SqlConnection sqlconn = new SqlConnection(connectionString);

            sqlconn.Open();

            SqlString = "select name from sys.databases where name NOT IN ('master', 'tempdb', 'model', 'msdb')";

            //加载数据并显示

           //string query = "SELECT name from sys.databases where name NOT IN ('master', 'tempdb', 'model', 'msdb')";

            try
            {
                MessageBox.Show("数据库连接成功！");
                //查询条件和SqlConnection连接
                SqlCommand cmd = new SqlCommand(SqlString, sqlconn);
                //数据适配器
                SqlDataAdapter sda = new SqlDataAdapter();
                sda.SelectCommand = cmd;
                //DataTable存储数据
                DataTable dt = new DataTable();
                sda.Fill(dt);
                dataGridView1.DataSource = dt;
                              
            }
           
            catch (Exception ex)
            {
                MessageBox.Show("数据库连接失败，请填写准确连接参数");
                return;
            }

            finally
            {
                conn.Close();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            String connectionString = String.Format("server={0};uid={1};pwd={2};", textBoxHost.Text, textBoxUser.Text, textBoxPassword.Text);
            
            SqlConnection sqlconn = new SqlConnection(connectionString);

            sqlconn.Open();

            SqlString = "SELECT a.name, b.rows FROM sysobjects AS a INNER JOIN sysindexes AS b ON a.id = b.id WHERE (a.type = 'u') AND (b.indid IN (0, 1)) ORDER BY b.rows desc";

            //加载数据并显示

            try
            {
                //查询条件和SqlConnection连接
                SqlCommand cmd = new SqlCommand(SqlString, sqlconn);
                //数据适配器
                SqlDataAdapter sda = new SqlDataAdapter();
                sda.SelectCommand = cmd;
                //DataTable存储数据
                DataTable dt = new DataTable();
                sda.Fill(dt);
                dataGridView1.DataSource = dt;

            }
            catch
            { }
            finally
            {
                conn.Close();
            }
        }

```

该回答引用GPTᴼᴾᴱᴺᴬᴵ
根据您提供的代码，可以在comboBox控件的SelectedIndexChanged事件中获取选择的数据库名称，并修改查询语句，以获取该数据库中各表的行数。代码示例如下：

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    string selectedDatabase = comboBox1.SelectedItem.ToString();
    String connectionString = String.Format("server={0};uid={1};pwd={2};database={3};", textBoxHost.Text, textBoxUser.Text, textBoxPassword.Text, selectedDatabase);

    SqlConnection sqlconn = new SqlConnection(connectionString);

    sqlconn.Open();

    SqlString = "SELECT a.name, b.rows FROM " + selectedDatabase + ".dbo.sysobjects AS a INNER JOIN " + selectedDatabase + ".dbo.sysindexes AS b ON a.id = b.id WHERE (a.type = 'u') AND (b.indid IN (0, 1)) ORDER BY b.rows desc";

    //加载数据并显示

    try
    {
        //查询条件和SqlConnection连接
        SqlCommand cmd = new SqlCommand(SqlString, sqlconn);
        //数据适配器
        SqlDataAdapter sda = new SqlDataAdapter();
        sda.SelectCommand = cmd;
        //DataTable存储数据
        DataTable dt = new DataTable();
        sda.Fill(dt);
        dataGridView1.DataSource = dt;

    }
    catch
    { }
    finally
    {
        sqlconn.Close();
    }
}

在这个代码中，我们修改了查询语句，使用了所选择的数据库名来动态构建查询语句，获取所选数据库内各表的行数。然后，我们将查询结果显示在DataGridView控件中，与之前的查询逻辑相同。