how to create dynamic Entity Framework query. where we are getting dbset name from user as parameter and othere condition like column names and other where clause conditions
Disclaimer: I'm the owner of Eval-Expression.NET
This library lets you evaluate, compile, and execute code at runtime. Almost all the C# language is supported.
You can find some example for LINQ Dynamic here: http://eval-expression.net/linq-dynamic
But you can do more like specifying the dbset and condition
Example
string set = "Entity1";
string whereClause = "x.ID > 2";
// CREATE the expression
string expression = "ctx." + set + ".Where(x => " + whereClause + ").ToList();";
// USING a context variable
var ctx = new EntityContext();
var list1 = Eval.Execute(expression, new {ctx});
// USING a context in the expression
EvalManager.DefaultContext.RegisterType(typeof(EntityContext));
var list2 = Eval.Execute("var ctx = new EntityContext();" + expression);
Related
I want to call a Table Valued Function from entity framework, and have it return an IQueryable. The code I have is:
// Defines table-valued function, which must return IQueryable<T>.
[Function(FunctionType.TableValuedFunction, nameof(ufnGetContactInformation), Schema = dbo)]
public IQueryable<ContactInformation> ufnGetContactInformation(
[Parameter(DbType = "int", Name = "PersonID")]int? personId)
{
ObjectParameter personIdParameter = personId.HasValue
? new ObjectParameter("PersonID", personId)
: new ObjectParameter("PersonID", typeof(int));
return this.ObjectContext().CreateQuery<ContactInformation>(
$"[{nameof(this.ufnGetContactInformation)}](#{nameof(personId)})", personIdParameter);
}
However, I also want to be able to pass into the TVF a Table Valued Parameter (so I can pass a list of Id's into the TVF). I've found code that can do this using a DataTable which references the user-defined type I have in the db, eg:
var dt = new DataTable();
dt.Columns.Add("Id");
dt.Rows.Add(1);
dt.Rows.Add(2);
dt.Rows.Add(3);
var idList = new SqlParameter("idList", SqlDbType.Structured);
warnings.Value = dt;
warnings.TypeName = "dbo.udt_idList";
entities.ExecuteStoredProcedure("usp_TableValuedFunc", idList);
The problem is, the second code uses SQLParameter, and the first code uses ObjectParameter. It appears that ObjectParameter won't allow for user-defined-types to be supplied, and any code EF uses that accepts SQLParameter won't allow me to return an IQueryable from a TVF. Any ideas, am I missing something?
I did raw SQL query below to select only certain fields from a table.
{
List<CustEmpVM> CustomerVMlist = new List<CustEmpVM>();
var cid = db.Customers.SqlQuery("select SchedDate from Customer where CustID = '#id'").ToList<Customer>();
}
But i keep getting the error of:
System.Data.Entity.Core.EntityCommandExecutionException occurred in EntityFramework.SqlServer.dll but was not handled in user code
Additional information: The data reader is incompatible with the specified ALFHomeMovers.Customer. A member of the type, CustID, does not have a corresponding column in the data reader with the same name.
The exception message is pretty straightforward: the query expected to return full entity of Customer table but only SchedDate column returned, hence EF cannot done mapping other omitted columns including CustID.
Assuming Customers is a DbSet<Customer>, try return all fields from Customer instead:
// don't forget to include SqlParameter
var cid = db.Customers.SqlQuery("SELECT * FROM Customer WHERE CustID = #id",
new SqlParameter("id", "[customer_id]")).ToList();
If you want just returning SchedDate column, materialize query results and use Select afterwards:
var cid = db.Customers.SqlQuery("SELECT * FROM Customer WHERE CustID = #id",
new SqlParameter("id", "[customer_id]"))
.AsEnumerable().Select(x => x.SchedDate).ToList();
NB: I think you can construct LINQ based from the SELECT query above:
var cid = (from c in db.Customers
where c.CustID == "[customer_id]"
select c.SchedDate).ToList();
Similar issue:
The data reader is incompatible with the specified Entity Framework
Use below query instead of raw query:
{
List<CustEmpVM> CustomerVMlist = new List<CustEmpVM>();
var cid = db.Customers.Where(w=>w.Id == YOURCUSTOMERID).Select(s=>new Customer{SchedDate = s.SchedDate }).ToList();
}
It will give compile time error rather than run time error.
I am trying to query my database to get a specific data from my database. however when I convert the query to string it doesn't return the select value, instead it returns the whole SQL Query in a string. I am stumped on why this is happening
public ActionResult StudiedModules()
{
Model1 studiedModules = new Model1();
List<StudiedModulesModel> listModules = new List<StudiedModulesModel>();
using (EntityOne context = new EnitityOne())
{
foreach(var module in context.StudiedModules){
studiedModules.School = context.ModuleDatas.Where(p=>p.ModuleCode == module.ModuleCode).Select(u=>u.School).ToString();
studiedModules.Subject = context.ModuleDatas.Where(p=>p.ModuleCode == module.ModuleCode).Select(u=>u.Subject).ToString();
}
}
var data = listModules;
return View(data);
}
Calling ToString() on an Entity Framework Linq query like that will in fact return the SQL Query. So as it's written, your code is doing exactly what you wrote it to do.
If you want to select the first result from the IQueryable<T>, then you need to call First() before your ToString(). So, try changing
studiedModules.School = context.ModuleDatas.Where(p=>p.ModuleCode == module.ModuleCode).Select(u=>u.School).ToString();
studiedModules.Subject = context.ModuleDatas.Where(p=>p.ModuleCode == module.ModuleCode).Select(u=>u.Subject).ToString()
to
studiedModules.School = context.ModuleDatas.Where(p=>p.ModuleCode == module.ModuleCode).Select(u=>u.School).First().ToString();
studiedModules.Subject = context.ModuleDatas.Where(p=>p.ModuleCode == module.ModuleCode).Select(u=>u.Subject).First().ToString()
There are a whole lot more methods available depending on what you're trying to accomplish. If you want to get a list, use ToList(), or as Uroš Goljat pointed out, you can get a comma-separated list of values using the Aggregate( (a, b)=> a + ", " + b) method.
How about using Aggregate( (a, b)=> a + ", " + b) instead of ToString().
Regards,
Uros
Majority of our tables in our models has a field called "intConcurrencyID" that we intended to use for concurrency checking. I believe the only way to enable this field for concurrency checking in a Database First environment is to set the Concurrency Mode to Fixed.
However, if we have huge numbers of tables per EDMX, we will have a hard time manually configuring each type per entity not to mention the possibility of some entities to be overlooked.
Do you have any ideas on how I can automate this process? It seems that T4 Template is not the way to go since the Concurrency Mode is in the CSDL not in the Code Behind..
I looked at the edmx file before and after changing a property's concurrency mode and came up with a solution as a console app which parses the edmx file starting with the storage model for 'timestamp' columns and modifies the conceptual model by following the mappings. This is a fairly robust solution, but it has some caveats.
I'm using MSSQL 2008, for which the timestamp/rowversion is the defacto concurrency type. In my models I only use this type as a concurrency token. If you use it in other places, but have a consistent name used for all concurrency tokens instead, I've included code for this scenario that can be uncommented. If you simply use a different concurrency type and that type is unique to concurrency columns, you can change the type from 'timestamp' in this line of code:
IEnumerable<XElement> storageEntities =
from el in ssdl.Descendants(XName.Get("EntityType",ssdlNS))
where (from prop in el.Elements(XName.Get("Property",ssdlNS)) where prop.Attribute("Type").Value == "timestamp" select prop).Count()>0
select el;
If your concurrency pattern is more complicated, this code won't suffice.
That being said, I whipped this up in about an hour and ran it and it worked great for me on a model with nearly 200 entities, saving me a lot of annoyance going through the sluggish edmx designer, so I'm sure others will benefit. This is a console application so you can put this in the prebuild step of your model project to integrate it into your build process.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml;
using System.Xml.Linq;
namespace ConfigureConcurrency
{
class Program
{
static void Main(string[] args)
{
string edmxPath = args[0]; //or replace with a fixed path
if (edmxPath == null || edmxPath.Length == 0)
return;
string edmxNS = #"http://schemas.microsoft.com/ado/2008/10/edmx";
string ssdlNS = #"http://schemas.microsoft.com/ado/2009/02/edm/ssdl";
string csdlNS = #"http://schemas.microsoft.com/ado/2008/09/edm";
string mapNS = #"http://schemas.microsoft.com/ado/2008/09/mapping/cs";
XElement root = XElement.Load(edmxPath);
//Storage Model
XElement ssdl = root.Descendants(XName.Get("StorageModels", edmxNS)).FirstOrDefault();
//Conceptual
XElement csdl = root.Descendants(XName.Get("ConceptualModels", edmxNS)).FirstOrDefault();
//Mapping
XElement map = root.Descendants(XName.Get("Mappings", edmxNS)).FirstOrDefault();
/*
Use this code instead of the line below it, if the type of your concurrency columns is used on other non-concurrency columns
and you use the same name for every concurrency column
string ConcurrencyColumnName = "RowVersion";
IEnumerable<XElement> storageEntities =
from el in ssdl.Descendants(XName.Get("EntityType", ssdlNS))
where (from prop in el.Elements(XName.Get("Property", ssdlNS)) where prop.Attribute("Name").Value == ConcurrencyColumnName select prop).Count() > 0
select el;
*/
IEnumerable<XElement> storageEntities =
from el in ssdl.Descendants(XName.Get("EntityType",ssdlNS))
where (from prop in el.Elements(XName.Get("Property",ssdlNS)) where prop.Attribute("Type").Value == "timestamp" select prop).Count()>0
select el;
//for each timestamp column, find the mapping then find the conceptual model property and establish the concurrency mode
foreach(XElement storageEntity in storageEntities)
{
//Get the mapping
XElement mapping = (from el in map.Descendants(XName.Get("EntityTypeMapping",mapNS)) where el.Element(XName.Get("MappingFragment",mapNS)).Attribute("StoreEntitySet").Value == storageEntity.Attribute("Name").Value select el).FirstOrDefault();
if (mapping != null)
{
//Get the column mapping
XElement column = (from el in storageEntity.Descendants(XName.Get("Property",ssdlNS)) where el.Attribute("Type").Value == "timestamp" select el).FirstOrDefault();
string columnName = column.Attribute("Name").Value;
XElement columnMapping = (from el in mapping.Descendants(XName.Get("ScalarProperty",mapNS)) where el.Attribute("ColumnName").Value == columnName select el).FirstOrDefault();
string propertyName = columnMapping.Attribute("Name").Value;
//Get the conceptual schema namespace and type name
string[] split = mapping.Attribute("TypeName").Value.Split('.');
string ns="", typeName =split[split.Length-1];
for (int i = 0; i < split.Length-1; i++)
{
if (i>0)
ns+=".";
ns += split[i];
}
//Find the entry in the conceptual model
XElement schema = (from el in csdl.Elements(XName.Get("Schema",csdlNS)) where el.Attribute("Namespace").Value == ns select el).FirstOrDefault();
if (schema != null)
{
//Find the entity type
XElement entity = (from el in schema.Descendants(XName.Get("EntityType",csdlNS)) where el.Attribute("Name").Value == typeName select el).FirstOrDefault();
//Find the property
XElement concurrencyProperty = (from el in entity.Elements(XName.Get("Property",csdlNS)) where el.Attribute("Name").Value == propertyName select el).FirstOrDefault();
//Set concurrency mode to fixed
concurrencyProperty.SetAttributeValue("ConcurrencyMode", "Fixed");
}
}
}
//Save the modifications
root.Save(edmxPath);
}
}
}
Solved my similar problem with the above console app.
But if you are running a later version of Entity Framework, be sure to update references to schemas. I am using EF 5 and for me I used the following lines:
string edmxNS = #"http://schemas.microsoft.com/ado/2009/11/edmx";
string ssdlNS = #"http://schemas.microsoft.com/ado/2009/11/edm/ssdl";
string csdlNS = #"http://schemas.microsoft.com/ado/2009/11/edm";
string mapNS = #"http://schemas.microsoft.com/ado/2009/11/mapping/cs";
Is there an equivalent for the following?
// convert model to dynamic (this is how the model is coming in)
IEnumerable<dynamic> dynmodel = (IEnumerable < dynamic >)Model;
// dynamic lambda ???
string col = "x.Name";
var grid = new WebGrid(source: dynmodel.OrderBy(x => #col)); // Doesn't resolve but need an equivalent here!!!
There is a project out there called Dynamic LINQ.
http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx