SQL insert command only working once in a loop

Question

This is s for loop and it will go to the times and will put the time column as true. This works for the first time, but when the time increases by 0.5, it stays false. The for loop is working as i tried a MessageBox.Show("" + Time1 + ""); inside the for loop.

for (double Time = time_began_5; Time < time_finished_5; Time = Time + 0.5)
        {
            string Time1 = Time.ToString("0.00");


            try
            {
                SqlConnection cn = new SqlConnection("Data Source=.\\SqlExpress;Initial Catalog=AllensCroft;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFramework;");

                cn.Open();
                SqlCommand Command = new SqlCommand("INSERT INTO Slots ([Date],[RoomID],[" + Time1 + "]) Values (@date,@room,1)", cn);
                Command.Parameters.AddWithValue("date", date);
                Command.Parameters.AddWithValue("room", rooms_combo.SelectedValue);

                Command.ExecuteNonQuery();


                try
                {
                    cn.Close();
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.ToString());
                }

            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }

        }

Here is what the database looks like, the first true field works, but when it loops to another time, it remains false, I think it may be due to the fact that if I have an existing row with that date (date is primary key), i cannot update that row, so i might need to have an IF the row exists, update, else create a new row.

Answer 1

Try this, you don't have to open connection in each loop, create your sql statement first looping through each value and then do insert using one statement

private string CreateInsertStatement(double time_began_5, double time_finished_5)
{
   string sql = "INSERT INTO Slots ([Date],[RoomID],";
   string valuesql = " Values (@date,@room,";
   for (double Time = time_began_5; Time < time_finished_5; Time = Time + 0.5)
   {
    string Time1 = Time.ToString("0.00");
    sql+ = "[" + Time1 + "],";
    valuesql+ = "1,";
   }
   sql = sql.TrimEnd(',') + ") ";
   valuesql = valuesql.TrimEnd(',') + ") ";

   return sql + valuesql;
}

private string CreateUpdateStatement(double time_began_5, double time_finished_5)
{
    string sql = "UPDATE Slots SET ";
    string wheresql = " WHERE [Date] = @date AND [RoomID] = @room";
    for (double Time = time_began_5; Time < time_finished_5; Time = Time + 0.5)
    {
        string Time1 = Time.ToString("0.00");
        sql+ = "[" + Time1 + "] = 1,";        
    }
    sql = sql.TrimEnd(','); 
    return sql + wheresql;
}

Then in you actual insert code:

try
{
    SqlConnection cn = new SqlConnection("Data Source=.\\SqlExpress;Initial Catalog=AllensCroft;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFramework;");

    cn.Open();
    SqlCommand Command;
    //check if row exists 
    Command = new SqlCommand("select count(*) from Slots WHERE [Date] = @date AND [RoomID] = @room", cn);
    Command.Parameters.AddWithValue("date", date);
    Command.Parameters.AddWithValue("room", rooms_combo.SelectedValue);

    var cnt = Command.ExecuteScalar();
    if(cnt!=null)
    {
        string sqlstr = ""
        if(Int32.Parse(cnt.ToString()) > 0)
        {
            sqlstr = CreateUpdateStatement(time_began_5,time_finished_5);
        }
        else if(Int32.Parse(cnt.ToString()) == 0)
        {
            sqlstr = CreateInsertStatement(time_began_5,time_finished_5);
        }
        Command = new SqlCommand(sqlstr, cn);
        Command.Parameters.AddWithValue("date", date);
        Command.Parameters.AddWithValue("room", rooms_combo.SelectedValue);
        Command.ExecuteNonQuery();
    }
    try
    {
        cn.Close();
    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }
}
catch (Exception e)
{
    Console.WriteLine(e.ToString());
}

Answer 2

You are doing an insert. In every loop you insert a new row and set the value true only for the column which name is equal to the current value of the variable Time1.

Not having a value for the other columns they probably default to false. (bit columns I suppose)

If you want a default to true for every column perhaps it is better to change the database schema adding the default for every time column, otherwise you need a long list of parameters

EDIT: If your logic dictates that you need only one row per date and set every time column to true if you enter the situation above then you can move this logic in the database using a stored procedure:

CREATE PROCEDURE InsertOrUpdateSlotFromCode(@dt smalldatetime, @roomID int)
AS
BEGIN
    DECLARE @cnt INT
    SELECT  @cnt = COUNT(*) from Slots WHERE [Date] = @dt
    if @cnt = 0 
        INSERT INTO Slots ([Date],[RoomID], <here all the time fields> VALUES (@dt, @roomID, 1, ....)
    else
        UPDATE Slots SET [09.00] = 1, ..... WHERE [Date] = @dt
    End 
END

then your code call the sp

using(SqlConnection cn = new SqlConnection(.........))
{
    cn.Open();
    SqlCommand Command = new SqlCommand("InsertOrUpdateSlotFromCode", cn);
    Command.CommandType = CommandType.StoredProcedure;
    Command.Parameters.AddWithValue("date", date);
    Command.Parameters.AddWithValue("room", rooms_combo.SelectedValue);
    Command.ExecuteNonQuery();
}

Of course now you can completely get rid of the loop