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")
Related
I'm trying to get column names of a table, but it only returns the column names such as TABLE_SCHEMA,TABLE_NAME,TABLE_CATALOG,TABLE_TYPE.
Here's the code;
DataTable table = con.GetSchema("Tables", new string[] { null, null, "Contact" });
var columnNames = (from DataRow r in table.Rows
from DataColumn c in table.Columns
select c.ColumnName).ToList();
I need to save the names in a list.Thanks.
try this:
DataTable table = con.GetSchema("Columns", new string[] { null, null, "Contact" });
you have to specify Columns instead of Tables as collectionName ...
you should also change your linq query to something like this:
var columnNames = (from r in tab.AsEnumerable()
select r.Field<string>("COLUMN_NAME")).ToList();
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, ...
In my code I have the following Linq Query:
IQueryable<Data> charts = (from report in ctx.Charts group report by new
{
Name = report.ChartTitle.ChartType.ChartCategory.CategoryName,
id = report.ChartTitle.ChartType.ChartCategory.ChartCategoryId,
Period = report.Period
} into d
select new Data
{
Name = d.Key.Name,
Id = d.Key.id,
Period = d.Key.Period,
Reports = from r in d group r by new
{ Title = r.ChartTitle.Name, id = r.ChartTitle.ChartTitleId } into rs
select new Report
{
Title = rs.Key.Title,
Id = rs.Key.id,
Charts = (from c in rs group c by new
{
ChartId = c.ChartId,
FiscalYear = c.FiscalYear,
ModifiedDate = c.ChartView.ModifiedDate,
Function = c.Function.DisplayName,
ChartData=c.ChartView.ViewData
} into cs
select new ChartInfo
{
ChartId = cs.Key.ChartId,
FiscalYear = cs.Key.FiscalYear,
ModifiedDate = cs.Key.ModifiedDate,
Function = cs.Key.Function,
ChartData=cs.Key.ChartData
})
}});
In the above code if I exclude the "ChartData" field (which is of XML datatype), the query executes fine. But when ever I include this field it throws the following error :"The xml data type cannot be selected as DISTINCT because it is not comparable."
Let me know what I am missing here?
You can't group by XML types. This is a SQL restriction, not a LINQ-to-SQL retriction. (See Group by on XML column field with LINQ and select an xml type column in select query with group by SQL Server 2008)
Do you need to group by the XML column? The alternative would be to group by your other columns and then select the first XML value as a result.
Charts = (from c in rs group c by new
{
ChartId = c.ChartId,
FiscalYear = c.FiscalYear,
ModifiedDate = c.ChartView.ModifiedDate,
Function = c.Function.DisplayName,
} into cs
select new ChartInfo
{
ChartId = cs.Key.ChartId,
FiscalYear = cs.Key.FiscalYear,
ModifiedDate = cs.Key.ModifiedDate,
Function = cs.Key.Function,
ChartData=cs.Value.FirstOrDefault().ChartData
})
When using LINQ-to-SQL the items being grouped are still accessible - you don't need to include every 'selected' property / column in the group by` clause like you would in SQL.
You did not tell us what is the actual datatype of the ChartData, but from the error you are describing it looks like the problem is that whatever this datatype is it does not implement the IComparable interface which is a required interface if you want instances of the datatype to be comparable
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));
Please help I am getting the following error when I am binding the drop down list in the form
Unable to cast object of type 'System.Data.Objects.ObjectQuery1[<>f__AnonymousType02[System.String,System.Int32]]' to type 'System.Collections.Generic.List`1
I have written the query in Linq language
return (IList )(from p in db.tbl_PRODUCT_CATEGORY
select new
{
catname = p.category_name,
catid = p.category_id,
});
I don't know whether it is correct
Please give me the correct format of the query
I think your query should look more like this:
return (IList)(from p in db.tbl_PRODUCT_CATEGORY select new { catname = p.category_name, catid = p.category_id, }).ToList();