报错了：string query1 = "SELECT 季度,COUNT(CASE WHEN 季度 = 'Q1' THEN 1 ELSE NULL END) AS Q1Count, COUNT(CASE WHEN 季度 = 'Q2' THEN 1 ELSE NULL END) AS Q2Count,COUNT(CASE WHEN 季度 = 'Q3' THEN 1 ELSE NULL END) AS Q3Count,COUNT(CASE WHEN 季度 = 'Q4' THEN 1 ELSE NULL END) AS Q4Count FROM FAIsum WHERE 审核年份 = @value3 GROUP BY 季度"; adapter.SelectCommand.Parameters.AddWithValue("@value3", dateTimePicker1.Text); SQLiteDataAdapter Myadapter1 = new SQLiteDataAdapter(query1, con); DataTable dtNEW = new DataTable(); Myadapter1.Fill(dtNEW); dataGridView1.DataSource = dtNEW; con.Close();

这个错误通常是由于在执行命令之前没有打开数据库连接所导致的。请检查你的代码，确保在执行查询之前先打开了数据库连接。具体的代码可能类似于：

using (var connection = new SQLiteConnection(connectionString))
{
    connection.Open();

    string query1 = "SELECT 季度,COUNT(CASE WHEN 季度 = 'Q1' THEN 1 ELSE NULL END) AS Q1Count, COUNT(CASE WHEN 季度 = 'Q2' THEN 1 ELSE NULL END) AS Q2Count,COUNT(CASE WHEN 季度 = 'Q3' THEN 1 ELSE NULL END) AS Q3Count,COUNT(CASE WHEN 季度 = 'Q4' THEN 1 ELSE NULL END) AS Q4Count FROM FAIsum WHERE 审核年份 = @value3 GROUP BY 季度";
    using (var command = new SQLiteCommand(query1, connection))
    {
        command.Parameters.AddWithValue("@value3", dateTimePicker1.Text);
        using (var adapter = new SQLiteDataAdapter(command))
        {
            DataTable dtNEW = new DataTable();
            adapter.Fill(dtNEW);
            dataGridView1.DataSource = dtNEW;
        }
    }
}

请注意，在这个例子中，我们使用了 using 语句来自动释放资源，并且在执行查询之前先打开了数据库连接。你需要将 connectionString 替换为你实际的连接字符串。