HI
I have an example document that looks like
<ItemEntry>
<PurchaseDate>2010-03-18T20:36:32.81108+13:00</PurchaseDate>
<StoreGUID>0a0324ad-5f99-486a-a2d0-870bc6991e9f</StoreGUID>
<ExpiryDate />
<CardID>111111</CardID>
<PurchaseAmount>0</PurchaseAmount>
<RedeemedAmount />
<EntryType>1</EntryType>
<RedeemedDate />
<SalesAssistantID>0</SalesAssistantID>
</ItemEntry>
As you can see there are couple of elements ExpiryDate and RedeemedDate are are empty.
var q = from c in xml.Elements("ItemEntry")
select new mdDetail {
PurchaseDate = (DateTime)c.Element("PurchaseDate"),
StoreGUID = (Guid)c.Element("StoreGUID"),
ExpiryDate = (DateTime?)c.Element("ExpiryDate")??DateTime.MinValue,
CardID = (int)c.Element("CardID"),
PurchaseAmount = (double)c.Element("PurchaseAmount"),
RedeemedAmount = (double?)c.Element("RedeemedAmount"),
EntryType = (int)c.Element("EntryType"),
RedeemedDate = (DateTime?)c.Element("RedeemedDate") ??DateTime.MinValue,
SalesAssistantID = (int)c.Element("SalesAssistantID"),
}
;
foreach (var item in q)
{
}
I am not sure how to deal with the null element value,
I have tried ??DateTime.MinValue and ??null however both give me a "
String was not recognized as a valid DateTime." error.
Any suggestions?
Thank you
ExpiryDate = String.IsNullOrEmpty((string)c.Element("ExpiryDate"))?
DateTime.MinValue : DateTime.Parse((string)c.Element("ExpiryDate"))
"You could also use null instead of DateTime.MinValue if ExpireyDate is
declared to be nullable"
#Gabe, you can't just use null - you need to use (DateTime?)null because the compiler won't know how to convert null into a DateTime object
So if you want the value to just be a blank (null) this would be the final code:
ExpiryDate = String.IsNullOrEmpty(c.Element("ExpiryDate").Value)?
(DateTime?)null : DateTime.Parse(c.Element("ExpiryDate").Value)
Assuming DateTime is a declared a nullable (DateTime?)
Related
I am trying to dynamically add rows to a datatable from a query expression result. However, I am getting the below exception :
"Cannot cast DBNull.Value to type 'System.Int16'. Please use a nullable type."
This is my code:
foreach (var linqItem in linqResult)
resultDT.Rows.Add(linqItem.GetType().GetProperties().Select(p => p.GetValue(linqItem, null)).ToArray());
Please help me figure out figure out this issue.
Additional Code:
var linqResult = from misDTRow in misUserDetailsDT.AsEnumerable()
join deptDTRow in departmentInfoDT.AsEnumerable()
on misDTRow.Field<Int16>("DepartmentID") equals deptDTRow.Field<Int32>("DeptID")
select
new
{
Username = misDTRow["LoginName"],
EmployeeID = misDTRow["EmployeeID"],
EmployeeName = misDTRow["EmployeeName"],
FoundIn = misDTRow["FoundIn"],
StatusInMIS = (bool)misDTRow["IsActive"] == true ? "Inactive" : "Active",
Department = deptDTRow["DeptName"]
};
DataTable Creation:
DataTable resultDT = new DataTable();
PropertyInfo[] propInfo = linqResult.First().GetType().GetProperties();
foreach (PropertyInfo property in propInfo)
resultDT.Columns.Add(property.Name, property.PropertyType);
I am creating the DataTable dynamically from the query result.
try change to int? instead of int
"Cannot cast DBNull.Value to type 'System.Int16'. Please use a nullable type."
this is because you trying to cast the nullable type to int.
Check your database table which column allow null. Then you can cast it to nullable type.
For example :
misDTRow.Field<Int?>("DepartmentID") equals deptDTRow.Field<Int?>("DeptID")
In sql server I create views where I can check for null values and replace them with a default if I want (i.e. ISNULL(PrimaryPhone, 'No Primary #') AS PrimaryPhone. I used a lot of views in my asp.net web forms application, but I am now learning MVC 4 and want to start out right.
I have a model, controller and view set up for my client table. I would like to be able to replace null/empty values with ("Not Entered") or something like that.
I believe this needs to go in the controller, please correct me if I'm wrong.
I saw an example that uses hasvalue, but it is not available through intellisense.
How would I replace empty/null values without using DefaultValue in my model?
Thanks
var result = db.Clients.Select(x => new
{
CustomerID = x.CustomerID,
UserID = x.UserID,
FullName = x.FullName,
EmailAdd = x.emailadd.DefaultIfEmpty("No Email"),....
You can use the ?? operator to set a default value when something is null:
var result = db.Clients.Select(x => new
{
CustomerID = x.CustomerID,
UserID = x.UserID,
FullName = x.FullName,
EmailAdd = x.emailadd ?? "No Email", ...
If you need more control, for example checking for both null and empty, you can also use the ?: operator (also known as the "conditional operator" or "ternary operator"):
var result = db.Clients.Select(x => new
{
CustomerID = x.CustomerID,
UserID = x.UserID,
FullName = x.FullName,
EmailAdd = string.IsNullOrEmpty(x.emailadd) ? "No Email" : x.emailadd, ...
Following Linq to Entities query is causing the "Unable to create a constant value of type 'Data.InhouseUnit'. Only primitive types ('such as Int32, String, and Guid') are supported in this context" exception.
IList<FaultReport> faultReports = (from fr in _session.FaultReports
where fr.CreatedOn > dateTime
select new FaultReport
{
Id = fr.Id,
ExecutionDate = fr.ExecutionDate ?? DateTime.MinValue,
FaultType = fr.FaultType,
Quarters = fr.Quarters,
InhouseSpaceId = fr.InhouseSpaceId,
InhouseSpace = new InhouseSpace { Id = fr.InhouseSpace.Id, Name = fr.InhouseSpace.Name },
InhouseUnitId = fr.InhouseUnitId ?? Guid.Empty,
**InhouseUnit = fr.InhouseUnitId == Guid.Empty ? null : new InhouseUnit { Id = fr.InhouseUnit.Id, Name = fr.InhouseUnit.Name }**
}).ToList();
Specifically, it is the if expression in bold font which causes the exception. I need to make the check as fr.InhouseUnitId is a nullable. If I take out the the bolded expression, the rest of the statement works just fine. I have spent a fair amount of time, in msdn forum and on web, to understand what is causing the exception but still cannot quite understand. Guid is scalar so it should work, right? Even this expression InhouseUnit = true ? null: new InhouseUnit() in place of the bolded expression in the above statement wouldn't work. Can we even write if/else
If i try to write an extension method to take away the logic and just return a result, following exception is thrown:
LINQ to Entities does not recognize the method 'System.Object
GuidConversion(System.Nullable`1[System.Guid], System.Object)' method, and this method
cannot be translated into a store expression
It looks like you are projecting into new objects of the same type that you are querying from. Is that the case? It seems a little weird, but assuming you have a good reason for doing this, you could split the query into two parts. The first part would get what you need from the database. The second part would run locally (i.e. LINQ-to-Objects) to give you the projection you need. Something like this:
var query =
from fr in _session.FaultReports
where fr.CreatedOn > dateTime
select new {
fr.Id,
fr.ExecutionDate,
fr.FaultType,
fr.Quarters,
InhouseSpaceId = fr.InhouseSpace.Id,
InhouseSpaceName = fr.InhouseSpace.Name,
InhouseUnitId = fr.InhouseUnit.Id,
InhouseUnitName = fr.InhouseUnit.Name,
};
IList<FaultReport> faultReports = (
from fr in query.ToList()
select new FaultReport {
Id = fr.Id,
ExecutionDate = fr.ExecutionDate ?? DateTime.MinValue,
FaultType = fr.FaultType,
Quarters = fr.Quarters,
InhouseSpaceId = fr.InhouseSpaceId,
InhouseSpace = new InhouseSpace { Id = fr.InhouseSpaceId, Name = fr.InhouseSpaceName },
InhouseUnitId = fr.InhouseUnitId ?? Guid.Empty,
InhouseUnit = fr.InhouseUnitId == Guid.Empty ? null : new InhouseUnit { Id = fr.InhouseUnitId, Name = fr.InhouseUnitName }
}).ToList();
I have a LinqToXML expression where I am trying to select distinct names based on similar attributes. The code is working great and I've put it below:
var q = xmlDoc.Element("AscentCaptureSetup").Element("FieldTypes")
.Descendants("FieldType")
.Select(c => new { width = c.Attribute("Width").Value,
script = c.Attribute("ScriptName").Value,
sqlType = c.Attribute("SqlType").Value,
enableValues = c.Attribute("EnableValues").Value,
scale = c.Attribute("Scale").Value,
forceMatch = c.Attribute("ForceMatch").Value,
forceMatchCaseSensitive = c.Attribute("ForceMatchCaseSensitive").Value,
sortAlphabetically = c.Attribute("SortAlphabetically").Value,
})
.Distinct();
The problem arises since not all the attributes are required, and if one of them is omitted, for example sortAlphabetically, I get an Object not Referenced error. Makes sense, but it there a way to alter the query to only use assign the new values if the attribute actually exists? (Thereby bypassing any null pointer errors)
Instead of using the Value property (which will blow up on a null reference), simply cast the XAttribute to string - you'll either get the value, or a null reference if the XAttribute reference is null. (XElement works the same way, and this applies to all conversions to nullable types.)
So you'd have:
.Select(c => new {
width = (string) c.Attribute("Width"),
script = (string) c.Attribute("ScriptName"),
sqlType = (string) c.Attribute("SqlType"),
enableValues = (string) c.Attribute("EnableValues"),
scale = (string) c.Attribute("Scale"),
forceMatch = (string) c.Attribute("ForceMatch"),
forceMatchCaseSensitive = (string) c.Attribute("ForceMatchCaseSensitive"),
sortAlphabetically = (string) c.Attribute("SortAlphabetically"),
})
Some of those attributes sound like they should actually be cast to int? or bool?, mind you...
I am having some trouble with a linq query I am trying to write.
I am trying to use the repository pattern without to much luck. Basically I have a list of transactions and a 2nd list which contains the description field that maps against a field in my case StoreItemID
public static IList<TransactionViewModel> All()
{
var result = (IList<TransactionViewModel>)HttpContext.Current.Session["Transactions"];
if (result == null)
{
var rewardTypes = BusinessItemRepository.GetItemTypes(StoreID);
HttpContext.Current.Session["Transactions"] =
result =
(from item in new MyEntities().TransactionEntries
select new TransactionViewModel()
{
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
}).ToList();
}
return result;
}
public static List<BusinessItemViewModel>GetItemTypes(int storeID)
{
var result = (List<BusinessItemViewModel>)HttpContext.Current.Session["ItemTypes"];
if (result == null)
{
HttpContext.Current.Session["ItemTypes"] = result =
(from items in new MyEntities().StoreItems
where items.IsDeleted == false && items.StoreID == storeID
select new BusinessItemViewModel()
{
ItemDescription = items.Description,
StoreID = items.StoreID,
StoreItemID = items.StoreItemID
}).ToList();
}
return result;
However I get this error
Unable to create a constant value of type 'MyMVC.ViewModels.BusinessItemViewModel'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
I know its this line of code as if I comment it out it works ok
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
How can I map ItemDescription against my list of itemTypes?
Any help would be great :)
This line has a problem:
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription,
Since you are using FirstOrDefault you will get null as default value for a reference type if there is no item that satifies the condition, then you'd get an exception when trying to access ItemDescription - either use First() if there always will be at least one match or check and define a default property value for ItemDescription to use if there is none:
ItemDescription = itemTypes.Any(r=>r.StoreItemID==item.StoreItemID)
? itemTypes.First(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription
: "My Default",
If itemTypes is IEnumerable then it can't be used in your query (which is what the error message is telling you), because the query provider doesn't know what to do with it. So assuming the that itemTypes is based on a table in the same db as TransactionEntities, then you can use a join to achieve the same goal:
using (var entities = new MyEntities())
{
HttpContext.Current.Session["Transactions"] = result =
(from item in new entities.TransactionEntries
join itemType in entities.ItemTypes on item.StoreItemID equals itemType.StoreItemID
select new TransactionViewModel()
{
ItemDescription = itemType.ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
CustomerName = rewards.CardID//TODO: Get customer name
}).ToList();
}
I don't know the structure of your database, but hopefully you get the idea.
I had this error due a nullable integer in my LINQ query.
Adding a check within my query it solved my problem.
query with problem:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.Equals(y.OBJ_ID));
query with problem solved:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.HasValue && s.Obj_Id.Value.Equals(y.OBJ_ID));