I am simply trying to derive an array[] using the following Linq query with EFF and Mysql:
DM_ItemGroup[] array =
(from item_grp in DbContext.hexa_item_group
join item_btn in DbContext.hexa_button
on item_grp.GroupID equals item_btn.ButtonID
where item_btn.ButtonType.Equals("G", StringComparison.Ordinal)
select new DM_ItemGroup
{
GroupID = SqlFunctions.StringConvert((decimal)item_grp.GroupID),
GroupName = item_grp.GroupName,
ButtonID = item_btn.ButtonID,
Default_TaxId = item_grp.Default_TaxId,
Out_Of_Sales = item_grp.Out_Of_Sales,
Sales_Seq = item_grp.Sales_Seq,
DataModel_Button = new DM_Button(),
}).ToArray<DM_ItemGroup>();
I initially tried .ToString() but it gave an exception. After trying SqlFunctions.StringConvert I am getting the following error:-
The specified method 'System.String StringConvert(System.Nullable`1[System.Decimal])'
on the type 'System.Data.Objects.SqlClient.SqlFunctions'
cannot be translated into a LINQ to Entities store expression.
How to convert the GroupID (which is a Int in my Table) to String (which is required by my DataModel)?
Thanks for down voting a perfectly legitimate question.Wish someone had answered the question with equal promptness.
I found the solution to my problem which is as follows:-
using (HexaEntities hh=new HexaEntities())
{
var cc = hh.hexa_item_group.ToDictionary(k => k.GroupID, k => k);
var lst = from l in cc
orderby l.Key
select new DM_ItemGroup {GroupID = l.Key.ToString(), GroupName = l.Value.GroupName, Default_TaxId=l.Value.Default_TaxId,ButtonID=l.Value.ButtonID.Value,Out_Of_Sales=l.Value.Out_Of_Sales,Sales_Seq=l.Value.Sales_Seq };
AllRecords = lst.ToList<DM_ItemGroup>();
}
Related
Need to sort/order a list of data based on an undetermined number of columns (1 or more).
What i'm trying to do is loop through the desired columns and add an OrderBy or ThenBy based on their number to the query'd list, but i'm unsuccessful...
Done this, but it doesn't compile:
var query = GetAllItems(); //returns a IQueriable list of items
//for each selected column
for (int i = 0; i < param.Columns.Length; i++)
{
if (i == 0)
{
query = query.OrderBy(x => x.GetType().GetProperty(param.Columns[i].Name));
}
else
{
//ERROR: IQueriable does not contain a definition for "ThenBy" and no extension method "ThenBy"...
query = query.ThenBy(x => x.GetType().GetProperty(param.Columns[i].Data));
}
}
How can i resolve this issue? Or any alternative to accomplish this requirement?
SOLUTION: #Dave-Kidder's solution is well thought and resolves the compile errors i had. Just one problem, OrderBy only executes (actually sorts the results) after a ToList() cast. This is an issue because i can't convert a ToList back to an IOrderedQueryable.
So, after some research i came across a solution that resolve all my issues.
Microsoft assembly for the .Net 4.0 Dynamic language functionality: https://github.com/kahanu/System.Linq.Dynamic
using System.Linq.Dynamic; //need to install this package
Updated Code:
var query = GetAllItems(); //returns a IQueriable list of items
List<string> orderByColumnList = new List<string>(); //list of columns to sort
for (int i = 0; i < param.Columns.Length; i++)
{
string column = param.Columns[i].Name;
string direction = param.Columns[i].Dir;
//ex.: "columnA ASC"
string orderByColumn = column + " " + direction;
//add column to list
orderByColumnList.Add(orderBy);
}
//convert list to comma delimited string
string orderBy = String.Join(",", orderByColumnList.ToArray());
//sort by all columns, yay! :-D
query.OrderBy(orderBy).ToList();
The problem is that ThenBy is not defined on IQueryable, but on the IOrderedQueryable interface (which is what IQueryable.OrderBy returns). So you need to define a new variable for the IOrderedQueryable in order to do subsequent ThenBy calls. I changed the original code a bit to use System.Data.DataTable (to get a similar structure to your "param" object). The code also assumes that there is at least one column in the DataTable.
// using System.Data.DataTable to provide similar object structure as OP
DataTable param = new DataTable();
IQueryable<DataTable> query = new List<DataTable>().AsQueryable();
// OrderBy returns IOrderedQueryable<TSource>, which is the interface that defines
// "ThenBy" so we need to assign it to a different variable if we wish to make subsequent
// calls to ThenBy
var orderedQuery = query.OrderBy(x => x.GetType().GetProperty(param.Columns[0].ColumnName));
//for each other selected column
for (int i = 1; i < param.Columns.Count; i++)
{
orderedQuery = orderedQuery.ThenBy(x => x.GetType().GetProperty(param.Columns[i].ColumnName));
}
you should write ThenBy after OrderBy like this:
query = query
.OrderBy(t=> // your condition)
.ThenBy(t=> // next condition);
I have two contexts. In one of them i have two views of which i get cods related to an entity from the another context. This query is taking too long time. How to improve it?
var negociacoes = _db.Negociacoes.Include(o=> o.User).ToArray();
var produtos = _oriDb.Vw_Produtos.ToArray();
var clientesVendedor = _oriDb.Vw_ClientesVendedores.ToArray();
var query = from n in negociacoes
join p in produtos on n.ProdutoId equals p.ProdutoId
join c in clientesVendedor on n.ClienteId equals c.codigo_entidade
select new NegociacaoView
{
NegociacaoId = n.NegociacaoId,
ProdutoId = n.ProdutoId,
Produto = p.descricao,
ClienteId = n.ClienteId,
Cliente = c.razao_social,
Rca = n.Rca,
Quantidade = n.Quantidade,
Preco = n.Preco,
Situacao = n.Situacao,
UserId = n.User.UserName,
Atendente = n.Atendente,
CondicaoId = n.CondicaoId,
DataCriacao = n.DataCriacao,
DataLiberacao = n.DataLiberacao,
Observacao = n.Observacao,
User = n.User
};
return query.ToList();
There are a couple of ways to speed this up:
It helps to run the smallest most efficient query first, then use those results to constrain the following queries.
Defining a select list so the database doesn't have to materialize every column will speed things up and use less memory.
Unfortunately, no matter how you do it in LINQ, you will end up with sql that uses large IN statements. A sproc would give you access to temp tables and joins that would be even better.
var negociacoes = _db.Negociacoes.Include(o=> o.User).ToArray();
//Use results of first query to constrain the second two. You could maybe combine the second two into one query.
var clientIds = negociacoes.Select(x => x.ClienteId);
var productIds = negociacoes.Select(x => x.ProdutoId);
var produtos = _oriDb.Vw_Produtos
.Where(x => productIds.Contains(x.ProdutoId))
//add a select. You're only using two columns from this table.
//.Select(x => new { })
.ToArray();
var clientesVendedor = _oriDb.Vw_ClientesVendedores
.Where(x => clientIds.Contains(x.codigo_entidade))
//add a select. You're only using two columns from this table.
//.Select(x => new { })
.ToArray();
var query = from n in negociacoes
join p in produtos on n.ProdutoId equals p.ProdutoId
join c in clientesVendedor on n.ClienteId equals c.codigo_entidade
select new NegociacaoView
{
NegociacaoId = n.NegociacaoId,
ProdutoId = n.ProdutoId,
Produto = p.descricao,
ClienteId = n.ClienteId,
Cliente = c.razao_social,
Rca = n.Rca,
Quantidade = n.Quantidade,
Preco = n.Preco,
Situacao = n.Situacao,
UserId = n.User.UserName,
Atendente = n.Atendente,
CondicaoId = n.CondicaoId,
DataCriacao = n.DataCriacao,
DataLiberacao = n.DataLiberacao,
Observacao = n.Observacao,
User = n.User
};
return query.ToList();
I'm trying to achieve dynamic filtering on a table. My UI has filters that can be enabled or disabled on demand, and as you can imagine, my query should be able to know when to add filters to the query.
What I have so far is that I check if the filter object has a value, and if it does it adds a where clause to it. Example:
var q1 = DBContext.Table1
if (!string.IsNullOrEmpty(filterModel.SubjectContains))
q1 = q1.Where(i => i.Subject.Contains(filterModel.SubjectContains));
if (filterModel.EnvironmentId != null)
q1 = q1.Where(i => i.EnvironmentId == filterModel.EnvironmentId);
if (filterModel.CreatedBy != null)
q1 = q1.Where(i => i.CreatedByUserId == filterModel.CreatedBy);
var final = q1.Select(i => new
{
IssuesId = i.IssuesId,
Subject = i.Subject,
EnvironmentId = i.EnvironmentId,
CreatedBy = i.CreatedByUser.FullName,
});
return final.ToList();
The code above generates T-SQL that contains a WHERE clause for each field that uses AND to combine the conditions. This is fine, and will work for most cases.
Something like:
Select
IssueId, Subject, EnvironmentId, CreatedById
From
Table1
Where
(Subject like '%stackoverflow%')
and (EnvironmentId = 1)
and (CreatedById = 123)
But then I have a filter that explicitly needs an IssueId. I'm trying to figure out how the EF Where clause can generate an OR for me. I'm looking something that should generate a Tsql that looks like this:
Select
IssueId, Subject, EnvironmentId, CreatedById
From
Table1
Where
(Subject like '%stackoverflow%')
and (EnvironmentId = 1)
and (CreatedById = 123)
or (IssueId = 10001)
Found a solution for this that doesn't have to do multiple database call and works for me.
//filterModel.StaticIssueIds is of type List<Int32>
if (filterModel.StaticIssueIds != null)
{
//Get all ids declared in filterModel.StaticIssueIds
var qStaticIssues = DBContext.Table1.Where(i => filterModel.StaticIssueIds.Contains(i.IssuesId));
//Let's get all Issues that isn't declared in filterModel.StaticIssueIds from the original IQueryable
//we have to do this to ensure that there isn't any duplicate records.
q1 = q1.Where(i => !filterModel.StaticIssueIds.Contains(i.IssuesId));
//We then concatenate q1 and the qStaticIssues.
q1 = q1.Concat(qStaticIssues);
}
var final = q1.Select(i => new
{
IssuesId = i.IssuesId,
Subject = i.Subject,
EnvironmentId = i.EnvironmentId,
CreatedBy = i.CreatedByUser.FullName,
});
return final.ToList();
I am somewhat new to expression trees and I just don't quite understand some things.
What I need to do is send in a list of values and select the columns for an entity from those values. So I would make a call something like this:
DATASTORE<Contact> dst = new DATASTORE<Contact>();//DATASTORE is implemented below.
List<string> lColumns = new List<string>() { "ID", "NAME" };//List of columns
dst.SelectColumns(lColumns);//Selection Command
I want that to be translated into code like this (Contact is an entity using the EF4):
Contact.Select(i => new Contact { ID = i.ID, NAME = i.NAME });
So let's say I have the following code:
public Class<t> DATASTORE where t : EntityObject
{
public Expression<Func<t, t>> SelectColumns(List<string> columns)
{
ParameterExpression i = Expression.Parameter(typeof(t), "i");
List<MemberBinding> bindings = new List<MemberBinding>();
foreach (PropertyInfo propinfo in typeof(t).GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
if (columns.Contains(propinfo.Name))
{
MemberBinding binding = Expression.Bind(propinfo, Expression.Property(i, propinfo.Name));
bindings.Add(binding);
}
}
Expression expMemberInit = Expression.MemberInit(Expression.New(typeof(t)), bindings);
return Expression.Lambda<Func<t, t>>(expMemberInit, i);
}
When I ran the above code I got the following error:
The entity or complex type 'Contact' cannot be constructed in a LINQ to Entities query.
I looked at the body of the query and it emitted the following code:
{i => new Contact() {ID = i.ID, NAME = i.NAME}}
I am pretty sure that I should be able to construct the a new entity because I wrote this line explicitly as a test to see if this could be done:
.Select(i => new Contact{ ID = i.ID, NAME = i.NAME })
This worked, but I need to construct the select dynamically.
I tried decompiling a straight query(first time I have looked at the low level code) and I can't quite translate it. The high level code that I entered is:
Expression<Func<Contact, Contact>> expression = z =>
new Contact { ID = z.ID, NAME = z.NAME };
Changing the framework used in the decompiler I get this code:
ParameterExpression expression2;
Expression<Func<Contact, Contact>> expression =
Expression.Lambda<Func<Contact, Contact>>
(Expression.MemberInit(Expression.New((ConstructorInfo) methodof(Contact..ctor),
new Expression[0]), new MemberBinding[] { Expression.Bind((MethodInfo)
methodof(Contact.set_ID), Expression.Property(expression2 = Expression.Parameter(typeof(Contact), "z"), (MethodInfo)
methodof(Contact.get_ID))), Expression.Bind((MethodInfo)
methodof(Contact.set_NAME), Expression.Property(expression2, (MethodInfo)
methodof(Contact.get_NAME))) }), new ParameterExpression[] { expression2
});
I have looked several places to try and understand this but I haven't quite gotten it yet. Can anyone help?
These are some places that I have looked:
msdn blog -- This is exactly what I want to do but my decopiled code soes not have Expression.Call.
msdn MemberInit
msdn Expression Property
stackoverflow EF only get specific columns -- This is close but this seems like it is doing the same thing as if i just use a select off of a query.
stackoverflow lambda expressions to be used in select query -- The answer here is exactly what I want to do, I just don't understand how to translate the decompiled code to
C#.
When I did it last time I projected result to not mapped class (not entity) and it worked, everything else was the same as in your code. Are you sure that not dynamic query like .Select(i => new Contact{ ID = i.ID, NAME = i.NAME }) works?
*Mongo Newbie here
I have a document containing several hundred numeric fields which I need to query in combination.
var collection = _myDB.GetCollection<MyDocument>("collection");
IMongoQuery mongoQuery; // = Query.GT("field", value1).LT(value2);
foreach (MyObject queryObj in Queries)
{
// I have several hundred fields such as Height, that are in queryObj
// how do I build a "boolean" query in C#
mongoQuery = Query.GTE("Height", Convert.ToInt16(queryObj.Height * lowerbound));
}
I have several hundred fields such as Height (e.g. Width, Area, Perimeter etc.), that are in queryObj how do I build a "boolean" query in C# that combines range queries for each field in conjunction.
I have tried to use the example Query.GT("field", value1).LT(value2);, however the compiler does not accept the LT(Value) construct. In any event I need to be able to build a complex boolean query by looping through each of the numeric field values.
Thanks for helping a newbie out.
EDIT 3:
Ok, it looks like you already have code in place to build the complicated query. In that case, you just needed to fix the compiler issue. Am assuming you want to do the following (x > 20 && x < 40) && (y > 30 && y < 50) ...
var collection = _myDB.GetCollection<MyDocument>("collection");
var queries = new List<IMongoQuery>();
foreach (MyObject queryObj in Queries)
{
//I have several hundred fields such as Height, that are in queryObj
//how do I build a "boolean" query in C#
var lowerBoundQuery = Query.GTE("Height", Convert.ToInt16(queryObj.Height * lowerbound));
var upperBoundQuery = Query.LTE("Height", Convert.ToInt16(queryObj.Height * upperbound));
var query = Query.And(lowerBoundQuery, upperBoundQuery);
queries.Add(query);
}
var finalQuery = Query.And(queries);
/*
if you want to instead do an OR,
var finalQuery = Query.Or(queries);
*/
Original Answer.
var list = _myDb.GetCollection<MyDoc>("CollectionName")
.AsQueryable<MyDoc>()
.Where(x =>
x.Height > 20 &&
x.Height < 40)
.ToList();
I have tried to use the example Query.GT("field", value1).LT(value2);,
however the compiler does not accept the LT(Value) construct.
You can query MongoDB using linq, if you are using the official C# driver. That ought to solve the compiler issue I think.
The more interesting question I have in mind is, how are you going to construct that complicated boolean query?
One option is to dynamically build an Expression and then pass that to the Where
My colleague is using the following code for something similar...
public static IQueryable<T> Where<T>(this IQueryable<T> query,
string column, object value, WhereOperation operation)
{
if (string.IsNullOrEmpty(column))
return query;
ParameterExpression parameter = Expression.Parameter(query.ElementType, "p");
MemberExpression memberAccess = null;
foreach (var property in column.Split('.'))
memberAccess = MemberExpression.Property
(memberAccess ?? (parameter as Expression), property);
//change param value type
//necessary to getting bool from string
ConstantExpression filter = Expression.Constant
(
Convert.ChangeType(value, memberAccess.Type)
);
//switch operation
Expression condition = null;
LambdaExpression lambda = null;
switch (operation)
{
//equal ==
case WhereOperation.Equal:
condition = Expression.Equal(memberAccess, filter);
lambda = Expression.Lambda(condition, parameter);
break;
//not equal !=
case WhereOperation.NotEqual:
condition = Expression.NotEqual(memberAccess, filter);
lambda = Expression.Lambda(condition, parameter);
break;
//string.Contains()
case WhereOperation.Contains:
condition = Expression.Call(memberAccess,
typeof(string).GetMethod("Contains"),
Expression.Constant(value));
lambda = Expression.Lambda(condition, parameter);
break;
}
MethodCallExpression result = Expression.Call(
typeof(Queryable), "Where",
new[] { query.ElementType },
query.Expression,
lambda);
return query.Provider.CreateQuery<T>(result);
}
public enum WhereOperation
{
Equal,
NotEqual,
Contains
}
Currently it only supports == && !=, but it shouldn't be that difficult to implement >= or <= ...
You could get some hints from the Expression class: http://msdn.microsoft.com/en-us/library/system.linq.expressions.expression.aspx
EDIT:
var props = ["Height", "Weight", "Age"];
var query = _myDb.GetCollection<MyDoc>("CName").AsQueryable<MyDoc>();
foreach (var prop in props)
{
query = query.Where(prop, GetLowerLimit(queryObj, prop), WhereOperation.Between, GetUpperLimit(queryObj, prop));
}
// the above query when iterated over, will result in a where clause that joins each individual `prop\condition` with an `AND`.
// The code above will not compile. The `Where` function I wrote doesnt accept 4 parameters. You will need to implement the logic for that yourself. Though it ought to be straight forward I think...
EDIT 2:
If you don't want to use linq, you can still use Mongo Query. You will just need to craft your queries using the Query.And() and Query.Or().
// I think this might be deprecated. Please refer the release notes for the C# driver version 1.5.0
Query.And(Query.GTE("Salary", new BsonDouble(20)), Query.LTE("Salary", new BsonDouble(40)), Query.GTE("Height", new BsonDouble(20)), Query.LTE("Height", new BsonDouble(40)))
// strongly typed version
new QueryBuilder<Employee>().And(Query<Employee>.GTE(x => x.Salary, 40), Query<Employee>.LTE(x => x.Salary, 60), Query<Employee>.GTE(x => x.HourlyRateToClients, 40), Query<Employee>.LTE(x => x.HourlyRateToClients, 60))