使用 C# 在变量中循环和存储来自 SQL Server 的数据

Question

I have a table similar to following in SQL

Code  Month Budget Expense 
A10   9     100    10
A10   10    100    40
A10   11    100    40 
A10   12    100    10

I would like to iterate through all the rows and store each set with the following variables:

variable_budget=100;
variable_month1 =10;
variable_month2 =40;
variable_month3 =40;
variable_month4 =10;

Please note that the month is not fixed but it can be 3 or 4 not more.

Please help me on a best strategy to achieve it.

Thank you

Answer 1

You have to use three basic classes to connect with SQL and receive data: SqlConnection , SqlCommand and SqlDataReader . Note that they are IDisposable , so using should be used :) Another way would be to use some ORM, like Entity Framework. Anyway, the first approach would be:

using (SqlConnection conn = new SqlConnection(MainData.ConnStr))
{
    conn.Open();
    using (SqlCommand com = new SqlCommand("select * from MY_TABLE", conn))
    using (SqlDataReader reader = com.ExecuteReader())
    {
        // check if query returned any rows, if so, loop through them
        if (reader.HasRows)
            while (reader.Read())
            {
                 //here you can do operations on table rows, like assigning to variables etc.
            }

    }
}

Answer 2

You try this,

 static void Main(string[] args)
                {
                    List<FrmDBSet> response = new List<FrmDBSet>();
                    response.Add(new FrmDBSet() {Code ="A10", Month=9,Budget=100,Expense=10 });
                    response.Add(new FrmDBSet() { Code = "A10", Month = 10, Budget = 100, Expense = 40 });
                    response.Add(new FrmDBSet() { Code = "A10", Month = 11, Budget = 100, Expense = 40 });
                    response.Add(new FrmDBSet() { Code = "A10", Month = 12, Budget = 100, Expense = 10 });

                    var res = response.GroupBy(s => s.Budget).ToDictionary(s => s.Key, s => s.ToList()).ToList();
                    FinalCls finalvalue = new FinalCls();

                    foreach (var item in res)
                    {
                        finalvalue.Budget = item.Key;              
                        int index = 1;
                        foreach (FrmDBSet value in item.Value)
                        {
                            string propertyname = $"variable_month{index}";
                            PropertyInfo property = finalvalue.GetType().GetProperty(propertyname);
                            if(property!=null)
                            property.SetValue(finalvalue, value.Expense);
                            index++;
                        }
                    }

                    Console.ReadKey();
                }

public class FinalCls
    {
        public int Budget { get; set; }
        public int variable_month1 { get; set; }
        public int variable_month2 { get; set; }
        public int variable_month3 { get; set; }
        public int variable_month4 { get; set; }
    }


    public class FrmDBSet
    {
        public string Code { get; set; }
        public int Month { get; set; }
        public int Budget { get; set; }
        public int Expense { get; set; }
    }