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'Expression of type 'System.String' cannot be used for parameter of type 'System.Reflection.PropertyInfo'

I have two classes - ContactCompany and inside List of ContactPeople.
The result must be - list of all contact people or a specific contact person that matches a certain criteria.
The criteria is a string and it will search all the string fields in both classes. If a ContactCompany is found , all the list of contact people will be displayed.
So Far I came up with this:
public List<ContactPersonDto> FilterContragentAndClients(string filter)
{
var contactCompanyStringProperties = typeof(ContactCompany).GetProperties().Where(prop => prop.PropertyType == filter.GetType() && prop.DeclaringType.Name != "AuditEntity`1");
var contactPersonStringProperties = typeof(ContactPerson).GetProperties().Where(prop => prop.PropertyType == filter.GetType());
var together = contactCompanyStringProperties.Concat(contactPersonStringProperties);
var allContactPersonFoundInCompany = this.contactCompanyRepository.GetAll(cc => contactCompanyStringProperties.Any
(prop => ((prop.GetValue(cc, null) == null) ? "" : prop.GetValue(cc, null).ToString().ToLower()) == filter)).SelectMany(acc => acc.ContactPeople).ToList();
var contactPersonOnItsOwn = contactPersonRepository.GetAll(cp => contactPersonStringProperties.Any
(prop => ((prop.GetValue(cp, null) == null) ? "" : prop.GetValue(cp, null).ToString().ToLower()) == filter));
var totalList = allContactPersonFoundInCompany.Concat(contactPersonOnItsOwn).Distinct().ToList().Take(100);
List<ContactPersonDto> result = new List<ContactPersonDto>();
foreach (var item in totalList)
{
result.Add(mapper.Map<ContactPersonDto>(item));
}
return result;
}
My idea was to check the property and its value, ToString() it and compare it with the criteria the user has inputted.
Just another note - I wrote the prop.Declarintype.Name in order to exclude AuditEntity properties.(Created By, Created At, etc.)
When I hit allContactPersonFoundInCompany the ToString() cannot be translated.
This is the full error I receive:
Expression of type 'System.String' cannot be used for parameter of type 'System.Reflection.PropertyInfo' of method 'Boolean Contains[PropertyInfo](System.Collections.Generic.IEnumerable`1[System.Reflection.PropertyInfo], System.Reflection.PropertyInfo)' (Parameter 'arg1')

I understood the implications of reflection , it is very slow, therefore here is my solution.
public List<ContactPersonDto> FilterContragentAndClients(string filter)
{
var contactPeopleInCompany = this.contactCompanyRepository.GetAll
(c => c.AccountablePerson.Contains(filter) |
c.Address.Contains(filter) ||
c.City.Contains(filter) ||
c.Name.Contains(filter) ||
c.Prefix.Contains(filter) ||
c.RegistrationNumber.Contains(filter)).SelectMany(c => c.ContactPeople);
var contactPerson = this.contactPersonRepository.GetAll
(cp => cp.Address.Contains(filter) ||
cp.Email.Contains(filter) ||
cp.Name.Contains(filter) ||
cp.PhoneNumber.Contains(filter) ||
cp.Prefix.Contains(filter));
var together = contactPeopleInCompany.Concat(contactPerson).Distinct().Take(100).ToList();
List<ContactPersonDto> result = new List<ContactPersonDto>();
foreach (var item in together)
{
result.Add(mapper.Map<ContactPersonDto>(item));
}
return result;
}

Clean way to check if all properties, except for two, matches between two objects? [duplicate]

This question already has answers here:
Comparing object properties in c# [closed]
(20 answers)
Closed 4 years ago.
I have a database containing components with about 20 properties. To find out if an update is needed I want to check if all properties for the two objects, except DateCreated and Id, matches.
If all matches no update, if not, update db.
Component comp_InApp = new Component()
{
Id = null,
Description = "Commponent",
Price = 100,
DateCreated = "2019-01-30",
// Twenty more prop
};
Component comp_InDb = new Component()
{
Id = 1,
Description = "Component",
Price = 100,
DateCreated = "2019-01-01",
// Twenty more prop
};
// Check if all properties match, except DateCreated and Id.
if (comp_InApp.Description == comp_InDb.Description &&
comp_InApp.Price == comp_InDb.Price
// Twenty more prop
)
{
// Everything up to date.
}
else
{
// Update db.
}
This works, but it's not a very clean way with 20 properties. Is there a better way of achieiving the same result in a cleaner way?

I am using DeepEqual when I don't want/don't have the time to write myself Equals and GetHashCode methods.
You can install it simply from NuGet with:
Install-Package DeepEqual
and use it like:
if (comp_InApp.IsDeepEqual(comp_InDb))
{
// Everything up to date.
}
else
{
// Update db.
}
But keep in mind that this will only work for your case when you want to explicitly compare objects, but not for the case when you want to remove an object form a List or cases like this, when Equals and GetHashCode are invoked.

One way, create a class that implements IEqualityComparer<Component> to encapsulate this logic and to avoid that you have modify the class Comparer itself(if you don't want this Equals logic all time). Then you can use it for a simple Equals of two instances of Component and even for all LINQ methods that accepts it as additional argument.
class ComponentComparer : IEqualityComparer<Component>
{
public bool Equals(Component x, Component y)
{
if (object.ReferenceEquals(x, y)) return true;
if (x == null || y == null) return false;
return x.Price == y.Price && x.Description == y.Description;
}
public int GetHashCode(Component obj)
{
unchecked
{
int hash = 17;
hash = hash * 23 + obj.Price.GetHashCode();
hash = hash * 23 + obj.Description?.GetHashCode() ?? 0;
// ...
return hash;
}
}
}
Your simple use-case:
var comparer = new ComponentComparer();
bool equal = comparer.Equals(comp_InApp, comp_InDb);
It works also if you have two collections and want to know the difference, for example:
IEnumerable<Component> missingInDb = inAppList.Except( inDbList, comparer );

Here is a solution with Reflection:
static bool AreTwoEqual(Component inApp, Component inDb)
{
string[] propertiesToExclude = new string[] { "DateCreated", "Id" };
PropertyInfo[] propertyInfos = typeof(Component).GetProperties()
.Where(x => !propertiesToExclude.Contains(x.Name))
.ToArray();
foreach (PropertyInfo propertyInfo in propertyInfos)
{
bool areSame = inApp.GetType().GetProperty(propertyInfo.Name).GetValue(inApp, null).Equals(inDb.GetType().GetProperty(propertyInfo.Name).GetValue(inDb, null));
if (!areSame)
{
return false;
}
}
return true;
}

You can use a Reflection but it may slow your application. An alternative way of creating that comparator is to generate it with Linq Expressions. Try this code:
public static Expression<Func<T, T, bool>> CreateAreEqualExpression<T>(params string[] toExclude)
{
var type = typeof(T);
var props = type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
.Where(p => !toExclude.Contains(p.Name))
.ToArray();
var p1 = Expression.Parameter(type, "p1");
var p2 = Expression.Parameter(type, "p2");
Expression body = null;
foreach (var property in props)
{
var pare = Expression.Equal(
Expression.PropertyOrField(p1, property.Name),
Expression.PropertyOrField(p2, property.Name)
);
body = body == null ? pare : Expression.AndAlso(body, pare);
}
if (body == null) // all properties are excluded
body = Expression.Constant(true);
var lambda = Expression.Lambda<Func<T, T, bool>>(body, p1, p2);
return lambda;
}
it will generate an expression that looks like
(Component p1, Component p2) => ((p1.Description == p2.Description) && (p1.Price == p2.Price))
Usage is simple
var comporator = CreateAreEqualExpression<Component>("Id", "DateCreated")
.Compile(); // save compiled comparator somewhere to use it again later
var areEqual = comporator(comp_InApp, comp_InDb);
EDIT: to make it more type safe you can exclude properties using lambdas
public static Expression<Func<T, T, bool>> CreateAreEqualExpression<T>(
params Expression<Func<T, object>>[] toExclude)
{
var exclude = toExclude
.Select(e =>
{
// for properties that is value types (int, DateTime and so on)
var name = ((e.Body as UnaryExpression)?.Operand as MemberExpression)?.Member.Name;
if (name != null)
return name;
// for properties that is reference type
return (e.Body as MemberExpression)?.Member.Name;
})
.Where(n => n != null)
.Distinct()
.ToArray();
var type = typeof(T);
var props = type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
.Where(p => !exclude.Contains(p.Name))
.ToArray();
/* rest of code is unchanged */
}
Now when using it we have an IntelliSense support:
var comparator = CreateAreEqualExpression<Component>(
c => c.Id,
c => c.DateCreated)
.Compile();

Get Entity Table Name - EF7

As the question states, anyone know how to get the entity table name in entity framework 7?
I have the code to do this in entity framework 6.1 (from another site, cant find link), but none of the interfaces/objects seem to be referenced in entity framework 7.
Code for EF6.1
public string GetTableName(Type type)
{
var metadata = ((IObjectContextAdapter)this).ObjectContext.MetadataWorkspace;
var objectItemCollection = ((ObjectItemCollection)metadata.GetItemCollection(DataSpace.OSpace));
var entityType = metadata.GetItems<EntityType>(DataSpace.OSpace).Single(e => objectItemCollection.GetClrType(e) == type);
var entitySet = metadata.GetItems(DataSpace.CSpace).Where(x => x.BuiltInTypeKind == BuiltInTypeKind.EntityType).Cast<EntityType>().Single(x => x.Name == entityType.Name);
var entitySetMappings = metadata.GetItems<EntityContainerMapping>(DataSpace.CSSpace).Single().EntitySetMappings.ToList();
EntitySet table = null;
var mapping = entitySetMappings.SingleOrDefault(x => x.EntitySet.Name == entitySet.Name);
if (mapping != null)
{
table = mapping.EntityTypeMappings.Single().Fragments.Single().StoreEntitySet;
}
else
{
mapping = entitySetMappings.SingleOrDefault(x => x.EntityTypeMappings.Where(y => y.EntityType != null).Any(y => y.EntityType.Name == entitySet.Name));
if (mapping != null)
{
table = mapping.EntityTypeMappings.Where(x => x.EntityType != null).Single(x => x.EntityType.Name == entityType.Name).Fragments.Single().StoreEntitySet;
}
else
{
var entitySetMapping = entitySetMappings.Single(x => x.EntityTypeMappings.Any(y => y.IsOfEntityTypes.Any(z => z.Name == entitySet.Name)));
table = entitySetMapping.EntityTypeMappings.First(x => x.IsOfEntityTypes.Any(y => y.Name == entitySet.Name)).Fragments.Single().StoreEntitySet;
}
}
return (string)table.MetadataProperties["Table"].Value ?? table.Name;
}

The only thing you need to do now to achieve the same is this:
public string GetTableName(Type type)
{
return this.Model.GetEntityType(type).SqlServer().TableName;
}
PS: I'm assuming this method is declared in your DbContext class, otherwise change the this keyword for your DbContext instance.
Update
GetEntityType was renamed to FindEntityType. You can find more info in this link
return this.Model.FindEntityType(type).SqlServer().TableName;

Search by multiple fields

I'm working on a project and implemented a search by multiple fields in MVC, using LINQ like so:
public ActionResult SearchResult(SearchViewModel model)
{
List<Requisition> emptyList = new List<Requisition>();
if (model.RequisitionID > 0
|| model.Department > 0
|| model.Status > 0
|| model.RequisitionedBy != null)
{
var results = db.Requisitions.Where(x => x.RequisitionId > 0);
results = ProcessSearchInput(model, results);
return PartialView(results.ToList());
}
return PartialView(emptyList);
}
Helper:
private static IQueryable<Requisition> ProcessSearchInput(SearchViewModel model, IQueryable<Requisition> results)
{
if (model.Department > 0)
results = results.Where(x => x.Department == model.Department);
if (model.RequisitionedBy != null)
results = results.Where(x => x.Requisitioned_By.Contains(model.RequisitionedBy));
if (model.Status > 0)
results = results.Where(x => x.Status.Contains(model.Status.ToString()));
return results;
}
This code works fine.
However, if I add an extra search field to the form, I would also need to add a separate if statement in the controller.
With the current approach, the ProcessSearchInput method will contain too many if statements.
Is there a better way to handle a search with multiple fields?

Your current approach violates the open closed principle. The solution is to create a dynamic filter like in this example. However that is a complicated solution that is worth only if you are going to add more and more filters along the way. If not then don't bother.

I agree with previous comments: your current solution is probably the way to go.
In the real world, you'll soon have to implement filters like 'all customers having either a billing- or a shipping-address in New York', and more complicated stuff. By then, all clever generic stuff will just be in the way.
However, if you promise never to use this in production code:
you can save a lot of typing by using a query by example, where you specify the filter as an instance of the type your source contains:
var example = new Requisition { Department = 8, Requisitioned_By ="john" };
var result = db.Requisitions.FilterByExample(example);
This is a simple implementation:
public static class FilterByExampleHelper
{
public static IQueryable<T> FilterByExample<T>(this IQueryable<T> source, T example) where T : class
{
foreach (var property in typeof(T).GetProperties(BindingFlags.Public|BindingFlags.Instance).Where(p => p.CanRead))
{
ConstantExpression valueEx = null;
var propertyType = property.PropertyType;
if (propertyType.IsValueType)
{
var value = property.GetValue(example);
if (value != null &&
!value.Equals(Activator.CreateInstance(propertyType)))
{
valueEx = Expression.Constant(value, propertyType);
}
}
if (propertyType == typeof(string))
{
var value = property.GetValue(example) as string;
if (!string.IsNullOrEmpty(value))
{
valueEx = Expression.Constant(value);
}
}
if (valueEx == null)
{
continue;
}
var parameterEx = Expression.Parameter(typeof(T));
var propertyEx = Expression.Property(parameterEx, property);
var equalsEx = Expression.Equal(propertyEx, valueEx);
var lambdaEx = Expression.Lambda(equalsEx, parameterEx) as Expression<Func<T, bool>>;
source = source.Where(lambdaEx);
}
return source;
}
}

Entity Framework throwing exception with Extension Method

I have the following code in my Controller:
public List<DockDoorViewModel> GetDoorViewModel()
{
List<DockDoorViewModel> doors = new List<DockDoorViewModel>();
for (int i = 1; i < 11; i++)
{
// This is where the Stack Trace is pointing to.
DockDoorViewModel door = db.vwDockDoorDatas
.Where(x => x.DockNo == i)
.Select(x => x.ToDockDoorViewModel())
.FirstOrDefault();
if (door == null)
{
door = new DockDoorViewModel(i);
}
else
{
door.Items = db.vwDockDoorDatas
.Where(x => x.DockNo == i)
.Select(x => x.ToDockDoorItem())
.ToList();
}
doors.Add(door);
}
return doors;
}
I am getting this exception when I try and Run the Web App:
Exception Details: System.NotSupportedException: LINQ to Entities does not recognize the method 'DockDoorMonitor.Models.DockDoorViewModel ToDockDoorViewModel(DockDoorMonitor.Models.vwDockDoorData)' method, and this method cannot be translated into a store expression.
Here is the extension method:
public static class vwDockDoorDataExtensions
{
public static DockDoorViewModel ToDockDoorViewModel(this vwDockDoorData x)
{
DockDoorViewModel vm = null;
if (x != null)
{
vm = new DockDoorViewModel()
{
ID = x.ID,
DockNo = x.DockNo,
loadType = x.loadType,
LoadDescription = x.LoadDescription,
Name = x.Name,
LocationCode = x.LocationCode,
SACode = x.SACode
};
}
return vm;
}
public static DockDoorItem ToDockDoorItem(this vwDockDoorData x)
{
DockDoorItem vm = null;
if (x != null)
{
vm = new DockDoorItem()
{
ID = x.ItemNo,
Description = x.Description,
Quantity = x.Quantity,
UnitOfMeasure = x.UnitOfMeasure
};
}
return vm;
}
}
I've done this kind of thing before so I'm not seeing what I am doing wrong? This is my first time with a MVC5 and EF6 application.

The error message tells you everything you need to know really - EF can't translate your extension methods to SQL therefore throws an exception. You need to convert your query from LINQ to Entities to LINQ to Objects, this can be done with a simple call to AsEnumerable() e.g.
DockDoorViewModel door = db.vwDockDoorDatas.Where(x => x.DockNo == i)
.AsEnumerable()
.Select(x => x.ToDockDoorViewModel())
.FirstOrDefault();
Effectively, what this does is create a hybrid query where everything before the AsEnumerable is translated and executed as SQL and the remainder being executed client-side and in memory.
As per your performance issues, looking at your query again you are unnecessarily pulling across a lot of records, you are only after the first one so why not just pull that one over i.e.
vwDockDoorData entity = db.vwDockDoorDatas.Where(x => x.DockNo == i)
.FirstOrDefault();
DockDoorViewModel door = entity != null ? entity.ToDockDoorViewModel() : null;
A further improvement on that would be to simply filter the records before you iterate them (give you have a start/end range) e.g.
var doorDatas = db.vwDockDoorDatas.Where(x => x.DockNo >= 1 && x.DockNo <= 11)
.ToList();
for (int i = 0; i < doorDatas.Count; i++)
{
// This is where the Stack Trace is pointing to.
DockDoorViewModel door = data.ToDockDoorViewModel();
if (door == null)
{
door = new DockDoorViewModel(i+1);
}
else
{
door.Items = data.ToDockDoorItem();
}
doors.Add(door);
}
The above would only require a single trip to the DB.

You will have to load the data from the SQL Server before using your to method. You can do this (for example) with the following command:
door.Items = db.vwDockDoorDatas
.Where(x => x.DockNo == i)
.ToList() //Possibly use AsEnumerable() here instead as James says
.Select(x => x.ToDockDoorItem())
.ToList();