可以通过以下步骤在c#代码中使用参数运行SQL查询：

1. 创建SqlConnection对象，连接到数据库。

2. 创建SqlCommand对象，设置SQL查询语句，并添加参数字符串。

   SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE Country = @Country", connection);

   command.Parameters.Add("@Country", SqlDbType.NVarChar).Value = "USA";

3. 执行查询并获取结果。

   SqlDataReader reader = command.ExecuteReader();

   while (reader.Read()) { Console.WriteLine(reader.GetString(0)); }

完整示例代码如下：

using System; using System.Data; using System.Data.SqlClient;

class Program { static void Main() { string connectionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";

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

        SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE Country = @Country", connection);
        
        command.Parameters.Add("@Country", SqlDbType.NVarChar).Value = "USA";

        SqlDataReader reader = command.ExecuteReader();

        while (reader.Read())
        {
            Console.WriteLine(reader.GetString(0));
        }
    }
}

}