How can I make DataTable enumerable?

问题:

I cannot use AsEnumerable() on DataTable, I'm using C# 3 but I'm just targeting 2.0 framework (LINQ capability is courtesy of LINQBridge). Is there any way I can make DataTable enumerable without using Select() ?

bool isExisting = (bdsAttachments.DataSource as DataTable).Select().Any(xxx => (string)dr["filename"] == filename);

Update:

I wanted it to make it look like this:

bool isExisting = (bdsAttachments.DataSource as DataTable).AsEnumerable().Any(xxx => (string)dr["filename"] == filename);

I'm getting an inkling that the Select method of DataTable returns a copy, I'm thinking to just use AsEnumerable, the problem is I'm just targeting 2.0 framework, System.Data.DataSetExtensions is not available

BTW, i tried this: http://cs.rthand.com/blogs/blog_with_righthand/archive/2006/01/15/284.aspx, but has compilation errors.

回答1:

    public static IEnumerable<DataRow> EnumerateRows(this DataTable table)
    {
        foreach (var row in table.Rows)
        {
            yield return row;
        }
    }

Allows you to call:

bool isExisting = (bdsAttachments.DataSource as DataTable).EnumerateRows().Any(dr => (string)dr["filename"] == filename);

回答2:

1. IEnumerable<DataRow> rows = dataTable.AsEnumerable(); (System.Data.DataSetExtensions.dll)
2. IEnumerable<DataRow> rows = dataTable.Rows.OfType<DataRow>(); (System.Core.dll)

回答3:

Keeping your enumerator strictly 2.0:

public static IEnumerable<DataRow> getRows(DataTable table)
{
    foreach (DataRow row in table.Rows)
    {
        yield return row;
    }
}

Then call with linqbridge like this:

bool isExisting = getRows(bdsAttachments.DataSource as DataTable).Any(row => (string)row["filename"] == filename);

回答4:

You can try casting the DataTable as IEnumerable and iterate over the set:

//your data exists as a DataTable
DataTable dt = (DataTable)bdsAttachments.DataSource;
foreach (DataRow row in dt)
{
    if (row["filename"] == filename)
        return row;
}

The foreach will iterate through the list and search of the filename (I assume you're searching for the first DataRow with that filename, not all rows that match the filename).