将由LINQ语句生成的字符串解析为方法

Question

I want to pass only e.Trip of my string.Format to the method referenced in tripChoose . As of now, it tried to pass a string not formatted for the method. If I could just pass the Trip part of the string, it would work. Any suggestions?

private void LoadExpenseListSums()
{
    expenseTotalSelect.Items.Clear();
    var sortedList=
        from e in roster
        group e by e.Trip into expenseCollect
        select new { Trip = expenseCollect.Key, SumAmount = expenseCollect.Sum(e => e.Amount) };
    foreach (var e in sortedList)
        tripChoose.Items.Add(string.Format("{0} | ${1}", e.Trip, e.SumAmount));
}

Answer 1

It looks like your expenseTotalSelect is an ASP.NET Select control and what you're doing ends up adding an element in the result HTML identified only by text such as:

<select id='expenseTotalSelect'>
    <option>Hawaii | $5000</option>
    <option>London | $4000</option>
    ...
</select>

In your expenseTotalSelect.Items.Add call you would probably be better off doing the following:

expenseTotalSelect.Items.Add(
       new ListItem(string.Format("{0} | ${1}", e.Trip, e.SumAmount),e.Trip));

Now you'll get the following when you render to HTML:

<select id='expenseTotalSelect'>
    <option value='Hawaii'>Hawaii | $5000</option>
    <option value='London'>London | $4000</option>
    ...
</select>

And it will be easier to just reference tripChoose.SelectedItem.Value which will only contain the e.Trip value (Hawaii or London) for this example

Answer 2

Right, now we actually know what we're dealing with, I suspect you want something like this:

private void LoadExpenseListSums()
{
    expenseTotalSelect.Items.Clear();
    var dateSorted =
        from e in roster
        group e by e.Trip into tripGroup
        select new { Trip = tripGroup.Key,
                     Text = string.Format("{0} | ${1}",
                                          tripGroup.Key,
                                          tripGroup.Sum(e => e.Amount) };
    tripChoose.DataSource = dateSorted;
    tripChoose.DisplayMember = "Text";
    tripChoose.ValueMember = "Trip";
}

This makes a few assumptions: ase, - roster is an in-memory collection: if it's not, you'll probably need an AsEnumerable call before the formatting, to make that happen locally - Anonymous types work with data binding; I'm not sure whether that's the case, but I'd hope it is

You then use the SelectedValue member later on to find the trip ID.

Answer 3

认为您应该使用注释中建议的对象，但假设expenseTotalSelect是List<string>并且tripChoose绑定到它，您可以这样做：

(string)tripChoose.SelectedItem.Split('|')[0].Replace(" ", string.Empty)