Another recurrence method

Question

Initially, I had the following:

[Flags]
public enum QueryFlag
{
    None = 0x00,
    CustomerID = 0x01,
    SalesPerson = 0x02,
    OrderDate = 0x04
}

When the checkboxes are checked or not checked, I would add / remove flags from:

QueryFlag qflag;

My idea is that when the user clicks the Search button, I will iterate over the actual flags set in qflagto change the sentence .Wherein my LINQ to Sql. However, it Enum.GetValues(qflag.GetType())returns all the values ​​of QueryFlag itself. Not healthy.

My decision:

class myForm : Form
{
    List<QueryFlag> qflag = new List<QueryFlag>();

    private void chkOrderDate_CheckedChanged(object sender, EventArgs e)
    {
        if (chkOrderDate.Checked && !qflags.Contains(QueryFlag.OrderDate))
            qflags.Add(QueryFlag.OrderDate);
        else
            qflags.Remove(QueryFlag.OrderDate);
    }

    private void cmdSearch_Click(object sender, EventArgs e)
    {
        if (qflags.Count == 0)
        {
            rtfLog.AppendText("\nNo search criteria selected.");
            return;
        }

        foreach (QueryFlag flag in qflag)
        {
            rtfLog.AppendText(string.Format("\nSearching {0}", flag.ToString()));

            // add switch for flag value
        }
    }
}

public enum QueryFlag
{
    CustomerID,
    SalesPerson,
    OrderDate
}

I have 3 checkboxes and this works without any problems. But I am wondering if there is a better way to accomplish this iteration.

Answer 1

, , ; Enum.GetValues. enum, . , , enum, , .

, :

private void chkOrderDate_CheckedChanged(object sender, EventArgs e)
{
    if (chkOrderDate.Checked)
    {
        qFlag |= QueryFlag.OrderDate;
    }
    else
    {
        qFlag &= (~QueryFlag.OrderDate);
    }
}

... CheckBoxes. , , :

static IEnumerable<QueryFlag> GetFlags(QueryFlag flags)
{
    foreach (QueryFlag flag in Enum.GetValues(typeof(QueryFlag)))
    {
        // Presumably you don't want to include None.
        if (flag == QueryFlag.None)
        {
            continue;
        }

        if ((flags & flag) == flag)
        {
            yield return flag;
        }
    }
}

enum:

public static class FlagsHelper
{
    // This is not exactly perfect, as it allows you to call GetFlags on any
    // struct type, which will throw an exception at runtime if the type isn't
    // an enum.
    public static IEnumerable<TEnum> GetFlags<TEnum>(this TEnum flags)
        where TEnum : struct
    {
        // Unfortunately this boxing/unboxing is the easiest way
        // to do this due to C# lack of a where T : enum constraint
        // (there are ways around this, but they involve some
        // frustrating code).
        int flagsValue = (int)(object)flags;

        foreach (int flag in Enum.GetValues(typeof(TEnum)))
        {
            if ((flagsValue & flag) == flag)
            {
                // Once again: an unfortunate boxing/unboxing
                // due to the lack of a where T : enum constraint.
                yield return (TEnum)(object)flag;
            }
        }
    }
}

, cmdSearch_Click :

private void cmdSearch_Click(object sender, EventArgs e)
{
    if (qFlag == QueryFlags.None)
    {
        rtfLog.AppendText("\nNo search criteria selected.");
        return;
    }

    foreach (QueryFlag flag in qFlag.GetFlags())
    {
        rtfLog.AppendText(string.Format("\nSearching {0}", flag.ToString()));

        // add switch for flag value
    }
}

Answer 2

, :

qflag.ToString().Split('|')