如何检查SQL数据库中的空列值，C#

using System;
using System.Data.SqlClient;

class Program
{
    static void Main()
    {
        string connectionString = "your_connection_string_here";
        string tableName = "your_table_name";
        string columnName = "your_column_name";

        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();

            string query = $"SELECT * FROM {tableName} WHERE {columnName} IS NULL";

            using (SqlCommand command = new SqlCommand(query, connection))
            {
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        Console.WriteLine($"Row ID: {reader["id"]}, Column Value: {reader[columnName]}");
                    }
                }
            }
        }
    }
}