i'm using the code below to delete the files that are more than 10 days old. Is there a simpler/smarter way of doing this?
string source_path = ConfigurationManager.AppSettings["source_path"];
string filename= ConfigurationManager.AppSettings["filename"];
var fileQuery= from file in Directory.GetFiles(source_path,filename,SearchOption.TopDirectoryOnly)
where File.GetCreationTime(file)<System.DateTime.Now.AddDays(-10)
select file;
foreach(var f in fileQuery)
{
File.Delete(f);
}
Well there are two things I'd change:
Determine the cut-off DateTime once, rather than re-evaluating DateTime.Now repeatedly
I wouldn't use a query expression when you've just got a where clause:
So I'd rewrite the query part as:
var cutoff = DateTime.Now.AddDays(-10);
var query = Directory.GetFiles(sourcePath, filename, SearchOption.TopDirectoryOnly)
.Where(f => File.GetCreationTime(f) < cutoff);
Another alternative would be to use DirectoryInfo and FileInfo:
var cutoff = DateTime.Now.AddDays(-10);
var path = new DirectoryInfo(sourcePath);
var query = path.GetFiles(filename, SearchOption.TopDirectoryOnly)
.Where(fi => fi.CreationTime < cutoff);
(In .NET 4 you might also want to use EnumerateFiles instead.)
It is possible to do a LINQ "one-liner" to perform this process:
Directory.GetFiles(source_path,filename,SearchOption.TopDirectoryOnly)
.Where(f => File.GetCreationTime(file) < System.DateTime.Now.AddDays(-10))
.All(f => {File.Delete(f); return true;);
Don't forget to wrap the code in a try catch.
Related
I have an array of string
var searchString = new string[] {"1:PS", "2:PS"};
and a large result string eg;
var largeString = "D9876646|10|1:PS^CD9876647100|11|2:PS"
how do I check if any of the options in searchString exist in the largeString?
I know it can be done via loop quite easily but I am looking for an other way around since I need to append the following as search clause in linq query.
You can use LINQ for it with a simple Any() call, like this:
var hasAny = searchString.Any(sub => largeString.Contains(sub));
However, this is as slow as a foreach loop. You can find the answer faster with a regex constructed from searchString:
var regex = string.Join("|", searchString.Select(Regex.Escape));
var hasAny = Regex.IsMatch(largeString, regex);
Depending on the nature of your LINQ provider (assuming it isn't LINQ to Objects), you may want to add individual tests for each member of searchString. The best way to do this is probably using PredicateBuilder
var sq = PredicateBuilder.New<dbType>();
foreach (var s in searchString)
sq = sq.Or(r => r.largeString.Contains(s));
q = q.Where(sq);
Is there an equivalent of right() function that I can use in jquery. I want to get records with fileextension xlsx.
new Guid(context.Documents.Where(T => T.FileName == ".xlsx").Select(T => T.ItemGuid).First().ToString());
something like
select * from document where right(filename,4) = 'xlsx'
I don't want to store the filename in a variable and later manipulate it. I want to be able to directly use it in my where condition. 'Documents' is my table name and "FileName" is a field that holds names of the file that I upload, now I need to get filter only the files that has the extension 'xlsx'. I tried doing
guid temp = new Guid(context.Documents.Where(T => T.FileName.Substring(T.FileName.Length - 4) == ".xlsm").Select(T => T.ItemGuid).First().ToString());
but I get the error "Sequence contains no elements" error.
* Update: Used the EndsWith() to get the information I wanted. This works now:
guid temp = new Guid(context.Documents.Where(T => T.FileName.EndsWith("xlsm")).Select(T => T.ItemGuid).First().ToString());
thanks.
filename.substr(-4)
Using .substr with a negative index will return a substring from the end of the string.
You can use .slice (MDN) function, taking into account that passing a negative value into it makes it cut the string from the end. )
var test = 'filename.xslx';
if (test.slice(-4) === 'xslx') {
alert("Passed");
}
right() is the same as endswith()
function endsWith(str, suffix) {
return str.indexOf(suffix, str.length - suffix.length) !== -1;
}
You might be looking for [name$="value"] selector documented here.
There is not, you can use
var filename = "file.xlsx";
var extension = filename.substr(filename.length - 4);
or to get the characters after the dot, you could use:
var extension = filename.split('.').pop();
Use could javascript match() which provides regex matching.
var filename = 'somefile.xlsx';
var matches = filename.match('/\.xlsx$/i');
if (matches.length > 0) {
// you have a match
}
I want to extract part of a collection to another collection.
I can easily do the same using a for loop, but my linq query is not working for the same.
I am a neophyte in Linq, so please help me correcting the query (if possible with explanation / beginners tutorial link)
Legacy way of doing :
Collection<string> testColl1 = new Collection<string> {"t1", "t2", "t3", "t4"};
Collection<string> testColl2 = new Collection<string>();
for (int i = 0; i < newLength; i++)
{
testColl2.Add(testColl1[i]);
}
Where testColl1 is the source & testColl2 is the desired truncated collection of count = newLength.
I have used the following linq queries, but none of them are working ...
var result = from t in testColl1 where t.Count() <= newLength select t;
var res = testColl1.Where(t => t.Count() <= newLength);
Use Enumerable.Take:
var testColl2 = testColl1.Take(newLength).ToList();
Note that there's a semantic difference between your for loop and the version using Take. The for loop will throw with IndexOutOfRangeException exception if there are less than newLength items in testColl1, whereas the Take version will silently ignore this fact and just return as many items up to newLength items.
The correct way is by using Take:
var result = testColl1.Take(newLength);
An equivalent way using Where is:
var result = testColl1.Where((i, item) => i < newLength);
These expressions will produce an IEnumerable, so you might also want to attach a .ToList() or .ToArray() at the end.
Both ways return one less item than your original implementation does because it is more natural (e.g. if newLength == 0 no items should be returned).
You could convert to for loop to something like this:
testColl1.Take(newLength)
Use Take:
var result = testColl1.Take(newLength);
This extension method returns the first N elements from the collection where N is the parameter you pass, in this case newLength.
I m trying to do something that look very simple but I hit massive difficulties when I want to make that more dynamic.
Expression<Func<TableServiceEntity, bool>> predicate = (e) => e.PartitionKey == "model" && (e.RowKey == "home" || e.RowKey == "shared");
context.CreateQuery<TableServiceEntity>(tableName).Where(predicate);
I would like to pass an array of rowKey instead of having to hard code the predicate.
When I try to build an expression tree I receive a not supported exception I think it doesn't support invoking as part of the expression tree.
Does someone know how to build and expression tree exactly as the predicate to avoid the not supported exception?
Thank you by advance
So, you can build the query dynamically by using something like this (taken from PhluffyFotos sample):
Expression<Func<PhotoTagRow, bool>> search = null;
foreach (var tag in tags)
{
var id = tag.Trim().ToLowerInvariant();
if (String.IsNullOrEmpty(id))
{
continue;
}
Expression<Func<PhotoTagRow, bool>> addendum = t => t.PartitionKey == id;
if (search == null)
{
search = addendum;
}
else
{
search = Expression.Lambda<Func<PhotoTagRow, bool>>(Expression.OrElse(search.Body, addendum.Body), search.Parameters);
}
}
Now, once you have 'search' you can just pass that as the predicate in your Where clause.
However, I want to convince you not to do this. I am answering your question, but telling you that it is a bad idea to do a multiple '|' OR clause in Table storage. The reason is that today at least, these queries cannot be optimized and they cause a full table scan. The performance will be horrendous with any non-trivial amount of data. Furthermore, if you build your predicates dynamically like this you run the risk of blowing the URL limit (keep that in mind).
This code in PhluffyFotos shows how, but it is actually a bad practice (I know, I wrote it). It really should be optimized to run each OR clause separately in parallel. That is how you really should do it. AND clauses are ok, but OR clauses should be parallelized (use PLINQ or TPL) and you should aggregate the results. It will be much faster.
HTH.
I believe what HTH said about this kind of query doing a full table scan is incorrect from the documentation I have read. Azure will perform a PARTITION scan rather than a TABLE scan which is a big difference in performance.
Here is my solution please read also the answer from HTH who pointed out that this is not a best practice.
var parameter = Expression.Parameter(typeof(TableServiceEntity), "e");
var getPartitionKey = typeof(TableServiceEntity).GetProperty("PartitionKey").GetGetMethod();
var getRowKey = typeof(TableServiceEntity).GetProperty("RowKey").GetGetMethod();
var getPartition = Expression.Property(parameter, getPartitionKey);
var getRow = Expression.Property(parameter, getRowKey);
var constPartition = Expression.Constant("model", typeof(string));
var constRow1 = Expression.Constant("home", typeof(string));
var constRow2 = Expression.Constant("shared", typeof(string));
var equalPartition = Expression.Equal(getPartition, constPartition);
var equalRow1 = Expression.Equal(getRow, constRow1);
var equalRow2 = Expression.Equal(getRow, constRow2);
var and = Expression.AndAlso(equalPartition, Expression.OrElse(equalRow1, equalRow2));
return Expression.Lambda<Func<TableServiceEntity, bool>>(and, parameter);
I've got a list of IQueryable. I'm trying to split this list into an array of IQueryable matching on a certain field (say fieldnum) in the first list...
for example, if fieldnum == 1, it should go into array[1]. I'm using Where() to filter based on this field, it looks something like this:
var allItems = FillListofMyObjects();
var Filtered = new List<IQueryable<myObject>(MAX+1);
for (var i = 1; i <= MAX; i++)
{
var sublist = allItems.Where(e => e.fieldnum == i);
if (sublist.Count() == 0) continue;
Filtered[i] = sublist;
}
however, I'm getting the error Field "t1.fieldnum" is not a reference field on the if line. stepping through the debugger shows the error actually occurs on the line before (the Where() method) but either way, I don't know what I'm doing wrong.
I'm farily new to LINQ so if I'm doing this all wrong please let me know, thanks!
Why don't you just use ToLookup?
var allItemsPerFieldNum = allItems.ToLookup(e => e.fieldnum);
Do you need to reevaluate the expression every time you get the values?
Why not use a dictionary?
var dictionary = allItems.ToDictionar(y => y.fieldnum);