Get value out of DateTime column
if null to return String.Empty
else
DateTime.ToShortDateString
What am I doing wrong => query produced below:
var queryable = from p in Products
select new {
selldate = p.SellEndDate == null
? string.Empty
: p.SellEndDate.Value.ToShortDateString() };
Error: InvalidOperationException: Could not translate expression 'Table(Product).Select(p => new <>f__AnonymousType01(selldate = IIF((p.SellEndDate = null), Invoke(value(System.Func1[System.String])), p.SellEndDate.Value.ToShortDateString())))' into SQL and could not treat it as a local expression.
Basically what's happening here is that LINQ to SQL is taking your entire query and trying to convert it into something that SQL Server can understand. The problem, though, is that SQL Server has no concept of DateTime.ToShortDateString, so the conversion to SQL fails.
You'll have to change your query so that it just selects SellEndDate (which will get it as a Nullable<DateTime>) and then when you use the results of that query you can do the conversion to string. For example:
var list = (from p in Products
select p.SellEndDate).ToList();
// calling ToList() above means we have the entire resultset in memory and
// no longer have to pass the query back to SQL Server
var stuff = from p in list select new
{
selldate = p.SellEndDate == null ?
string.Empty :
p.SellEndDate.Value.ToShortDateString()
};
ToShortDateString doesn't seem to have equivalent SQL translation.
Use ToString instead.
If the date time field allows nulls:
from order in repository.Order
select order.OrdShipDate == null ? "" : order.OrdShipDate.GetValueOrDefault(DateTime.Now).Month.ToString() + "/" + order.OrdShipDate.GetValueOrDefault(DateTime.Now).Day.ToString() + "/" + order.OrdShipDate.GetValueOrDefault(DateTime.Now).Year.ToString();
If the date time field doesn't allow nulls:
from order in repository.Order
select order.OrdShipDate.Month.ToString() + "/" + order.OrdShipDate.Day.ToString() + "/" + order.OrdShipDate.Year.ToString();
Related
I am trying to recreate the SQL condition of: like '1 %'.
The column in the table contains two sets of values separated by a space. Using StartsWith(glassTag) returns any row where the column starts with '1'. It seems to do a trim on the string before testing the condition. But, if I use StartsWith("1 "), it returns the rows I expect.
What am I doing wrong?
This is a LINQ to Entity question. SqlMethods are not compatible.
the following returns where the Name is: "119 GL-01"
var glassTag = "1 ";
var gItem = await _context.Items.Where(x => x.Name.StartsWith(glassTag) && x.Material.MaterialType.Name.Equals("Glass") && x.JobItems.Any(j => j.Job.Code.Equals(pCode))).ToListAsync();
The code below returns the results I expect
var gItem = await _context.Items.Where(x => x.Name.StartsWith("1 ") && x.Material.MaterialType.Name.Equals("Glass") && x.JobItems.Any(j => j.Job.Code.Equals(pCode))).ToListAsync();
StartsWith simply doesn't work for a variable being passed when looking for spaces at the end.
I have captured the sql being generated by EF.
The code below generates the sql directly below it. When passing a variable to the StartsWith condition, it doesn't use "like". And it creates something that isn't right.
var gItem = _context.Items.Where(x => x.Name.StartsWith(gd.glasstag + " "));
DECLARE #__glassTag_0 nvarchar(4000) = N'1 ';
SELECT [i].[ItemId], [i].[Name]
FROM [Item] AS [i]
WHERE (#__glassTag_0 = N'') OR ([i].[Name] IS NOT NULL AND (LEFT([i].[Name], LEN(#__glassTag_0)) = #__glassTag_0))
The code below generates the sql below it. Note, it uses the "like" condition.
var gItem = _context.Items.Where(x => x.Name.StartsWith("1 "));
SELECT [i].[ItemId], [i].[Name]
FROM [Item] AS [i]
WHERE [i].[Name] IS NOT NULL AND ([i].[Name] LIKE N'1 %')
So, I will be creating a stored procedure to retrieve the data I need. The code will look like this:
var glassTag = gd.glasstag + " ";
var gItem = await _context.Items.FromSqlRaw($"spItemsByGlassTag '{pCode}', '{glassTag}'").ToListAsync();
Im getting this error when I execute the following code, any Ideas how to fix it?
LINQ to Entities does not recognize the method 'Int32 Min(Int32, Int32)' method, and this method cannot be translated into a store expression.
result = items.ToList()
.Select(b => new BatchToWorkOnModel()
{
BatchID = b.Batch.ID,
SummaryNotes = b.Batch.Notes,
RowVersion = b.Batch.RowVersion,
Items = items
.Select(i => new ItemToWorkOnModel()
{
SupplierTitle = i.Title,
ItemID = i.ID,
BatchID = i.BatchID ?? 0,
ItemDate = i.PubDate,
// KB - Issue 276 - Return the correct Outlet name for each item
Outlet = i.Items_SupplierFields != null ? i.Items_SupplierFields.SupplierMediaChannel != null ? i.Items_SupplierFields.SupplierMediaChannel.Name : null : null,
Status = ((short)ItemStatus.Complete == i.StatusID ? "Done" : "Not done"),
NumberInBatch = i.NumInBatch,
Text = string.IsNullOrEmpty(i.Body) ? "" : i.Body.Substring(0, Math.Min(i.Body.Length, 50)) + (i.Body.Length < 50 ? "" : "..."),
IsRelevant = i.IsRelevant == 1,
PreviouslyCompleted = i.PreviouslyCompleted > 0 ? true : false
}).ToList()
})
.FirstOrDefault();
It seems Math.Min is not implemented by the EF query provider. You should be able to fix it by simply applying AsEnumerable on your items collection to do the expression using Linq to Objects instead;
Items = items.AsEnumerable().Select(i => new ItemToWorkOnModel()...
If you add a where condition to the item selection (seems a little strange to take all items in the whole table), you'll want to add it before AsEnumerable() to allow EF to do the filtering in the database.
Also, you only want the first result from the query, but you're fetching all of them using ToList() before cutting the list down to a single item. You may want to remove the ToList() so that EF/the underlying database can return only a single result;
result = items.Select(b => new BatchToWorkOnModel()...
You do not need Math.Min.
The line in question is:
Text = string.IsNullOrEmpty(i.Body)
? "" : i.Body.Substring(0, Math.Min(i.Body.Length, 50)) + (i.Body.Length < 50 ? "" : "...")
So what does this line return?
If i.Body is null or empty it returns an empty string. If it is 50 or more characters long it returns a substring of 50 characters and appends "...".
If the length is less than 50 it takes a substring with the length of the string and appends an empty string. But that's just the original string.
Text = string.IsNullOrEmpty(i.Body)
? "" : (i.Body.Length < 50 ? i.Body : i.Body.Substring(0, 50) + "...")
I am trying to take a DateTime value, and if it is not null return the Short Time String. My query looks like this:
(TimeIn is NOT NULLABLE, whereas TimeOut is NULLABLE)
var times = from t in db.TimePostings
where t.MemberID == member.MemberID
select new
{
Date = t.TimeIn.ToShortDateString(),
TimeIn = t.TimeIn.ToShortTimeString(),
TimeOut = t.TimeOut.HasValue ? t.TimeOut.Value.ToShortTimeString() : "-------"
};
gvTimePostings.DataSource = times;
gvTimePostings.DataBind();
but this fails when I try to databind with the error:
Could not translate expression 'Table(TimePosting).Where(t =>
(t.MemberID == Invoke(value(System.Func1[System.String])))).Select(t
=> new <>f__AnonymousType84(Date = t.TimeIn.ToShortDateString(), TimeIn = t.TimeIn.ToShortTimeString(), TimeOut =
IIF(t.TimeOut.HasValue, (t.TimeOut ??
Invoke(value(System.Func`1[System.DateTime]))).ToShortTimeString(),
"-------"), Hours = ""))' into SQL and could not treat it as a local
expression.
I also get a similar error if I try to use:
TimeOut = t.TimeOut.HasValue ? Convert.ToDateTime(t.TimeOut).ToShortTimeString() : "-------"
however, if I change the TimeOut property to:
TimeOut = t.TimeOut.HasValue ? t.TimeOut.ToString() : "-------",
it works fine, but does not format the time like I want it (shortTimeString).
what's up with that?
As others have said, the problem is with trying to convert ToShortDateString etc to SQL. Fortunately, this is easy to fix: fetch the data with SQL, then format it in .NET:
var timesFromDb = from t in db.TimePostings
where t.MemberID == member.MemberID
select new { t.TimeIn, t.TimeOut };
var times = from t in timesFromDb.AsEnumerable()
select new
{
Date = t.TimeIn.ToShortDateString(),
TimeIn = t.TimeIn.ToShortTimeString(),
TimeOut = t.TimeOut.HasValue
? t.TimeOut.Value.ToShortTimeString()
: "-------"
};
The call to AsEnumerable() here basically means, "stop trying to process the query using SQL; do the rest in LINQ to Objects".
ToShortTimeString() has no translation in SQL. Because of that, converting the statement into a single SQL statement fails and the exception is thrown.
If you break the statement into two calls (one to retrieve the data and another to create the projection), things will work just fine:
// must call ToList to force execution of the query before projecting
var results = from t in db.TimePostings
where t.MemberID == member.MemberID
select new { t.TimeIn, t.TimeOut };
var times = from t in results.AsEnumerable()
select new
{
Date = t.TimeIn.ToShortDateString(),
TimeIn = t.TimeIn.ToShortTimeString(),
TimeOut = t.TimeOut.HasValue ?
t.TimeOut.Value.ToShortTimeString() :
"-------"
};
Have you tried:
TimeOut = t.TimeOut.HasValue ? t.TimeOut.ToString("d") : "-------",
This will normally give the short format of the DateTime. Whether it works or not will depend on whether it can be translated to SQL or not.
If it doesn't work you'll have to break the query into two parts. The first gets the data, the second format it. You'll have to convert the first query to a list (.ToList()) to force the SQL to be evaluated.
Simply, it's not supported by this specific linq provider.
Your linq query is converted into an expression tree. It is up to the SQL Linq provider to convert this expression tree into SQL. Understandably, it does not have the capability to translate every single .NET function.
Your solution is to explicitly run the SQL by calling ToArray or ToList, and then allow LinqToObjects to handle the rest.
var times = from t in db.TimePostings
where t.MemberID == member.MemberID
select new {
TimeIn = t.TimeIn,
TimeOut = t.TimeOut
};
var timesFormated = times.ToArray() // Runs the query - any further processing will be run in memory by the local .NET code
.Select(t => new {
Date = t.TimeIn.ToShortDateString(),
TimeIn = t.TimeIn.ToShortTimeString(),
TimeOut = t.TimeOut.HasValue ? t.TimeOut.Value.ToShortTimeString() : "-------",
Hours = ""
}
);
Your query is transformed by LINQ to an SQL that is fired against your database, and there is obviously no way to translate t.TimeOut.Value.ToShortTimeString() to SQL.
Possible solutions are:
First fetch your data from database (by calling .ToList() or .ToArray() on your LINQ query), that converts your IQueryable<> into IEnumerable<> and then apply your transformation for every row fetched.
Use a view that takes the original table and performs the conversion using CONVERT() function on the SQL Server and use it as the source for your Linq-to-SQL class. That would be performanter, but requires some server-side changes.
I had the same problem in a project in vb.net.
The solution I've found is based on the use of:
if(table.field.hasvalue, table.field.value.ToShortDateString, string.format("NULL"))
In this case, if the selected field (table.field) has a value this is converted into a date string otherwise if the field hasn't a value the output field is filled with string "NULL"
I am new to LINQ, and I wish to convert from one datatype to another in C#, as well as concatenate a string. How would I accomplish this?
For example, what would the SQL statement
SELECT IPv4 = CONVERT(varchar(3), IPv4_octet1) + '.' +
CONVERT(varchar(3), IPv4_octet2) + '.' +
CONVERT(varchar(3), IPv4_octet3) + '.' +
CONVERT(varchar(3), IPv4_octet4) FROM table;
be in LINQ? (The IPv4_octet's are stored as tinyints in the SQL table.)
In this case I suspect you could just write:
var query = data.Select(x => x.IpV4Octet1 + "." +
x.IpV4Octet2 + "." +
x.IpV4Octet3 + "." +
x.IpV4Octet4);
More generally you'd call ToString, e.g.:
// You wouldn't want to actually do this, but...
var query = data.Select(x => x.IpV4Octet1.ToString() + x.IpV4Octet4.ToString());
If you want more control, and you're not using the result in the rest of the query, you may well want to do the formatting on the .NET side - simply use AsEnumerable when you've selected all the information you want from the database, and then do the rest in LINQ to Objects. For example:
var query = db.Select(x => new { x.HostName, x.IpV4Octet1, x.IpV4Octet2,
x.IpV4Octet3, IpV4Octet4 })
.AsEnumerable() // Switch to LINQ to Objects for rest of query
.Select(x => new { x.HostName,
Address = string.Format("{0}.{1}.{2}.{3}"),
x.IpV4Octet1,
x.IpV4Octet2,
x.IpV4Octet3,
x.IpV4Octet4) });
try this:
string ipv4 = string.Join('.',octets.Select(o => o.ToString()).ToArray());
I'm very new to Linq, I can find multi-line data reading examples everywhere (by using foreach()), but what is the correct way of reading a single line of data? Like a classic Product Detail page.
Below is what I tried:
var q = from c in db.Products
where c.ProductId == ProductId
select new { c.ProductName, c.ProductDescription, c.ProductPrice, c.ProductDate };
string strProductName = q.First().ProductName.ToString();
string strProductDescription = q.First().ProductDescription.ToString();
string strProductPrice = q.First().ProductPrice.ToString();
string strProductDate = q.First().ProductDate.ToString();
The code looks good to me, but when I see the actual SQL expressions generated by using SQL Profiler, it makes me scared! The program executed four Sql expressions and they are exactly the same!
Because I'm reading four columns from a single line. I think I must did something wrong, so I was wondering what is the right way of doing this?
Thanks!
Using the First() extension method would throw the System.InvalidOperationException when no element in a sequence satisfies a specified condition.
If you use the FirstOrDefault() extension method, you can test against the returned object to see if it's null or not.
FirstOrDefault returns the first element of a sequence, or a default value if the sequence contains no elements; in this case the default value of a Product should be null. Attempting to access the properties on this null object will throw ArgumentNullException
var q = (from c in db.Products
where c.ProductId == ProductId
select new { c.ProductName, c.ProductDescription, c.ProductPrice, c.ProductDate }).FirstOrDefault();
if (q != null)
{
string strProductName = q.ProductName;
string strProductDescription = q.ProductDescription;
string strProductPrice = q.ProductPrice;
string strProductDate = q.ProductDate;
}
Also, you shouldn't have to cast each Property ToString() if you're object model is setup correctly. ProductName, ProductDescription, etc.. should already be a string.
The reason you're getting 4 separate sql queries, is because each time you call q.First().<PropertyHere> linq is generating a new Query.
var q = (from c in db.Products
where c.ProductId == ProductId
select new { c.ProductName, c.ProductDescription, c.ProductPrice, c.ProductDate }
).First ();
string strProductName = q.ProductName.ToString();
string strProductDescription = q.ProductDescription.ToString();
string strProductPrice = q.ProductPrice.ToString();
string strProductDate = q.ProductDate.ToString();