How to Search through all fields in a LINQ table? - linq

Question

in LINQ how do i search all fields in a table, what do i put for ANYFIELD in the below?
Thanks
var tblequipments = from d in db.tblEquipments.Include(t => t.User).Include(t => t.ChangeLog).Include(t => t.AssetType)
where d."ANYFIELD" == "VALUE" select d;

Answer 1

You can't. You must compare each field individually. It doesn't make sense to compare all fields, given a field may not even be of the same type as the object you're comparing to.

Answer 2

You can, using reflection. Try this:
static bool CheckAllFields<TInput, TValue>(TInput input, TValue value, bool alsoCheckProperties)
{
Type t = typeof(TInput);
foreach (FieldInfo info in t.GetFields().Where(x => x.FieldType == typeof(TValue)))
{
if (!info.GetValue(input).Equals(value))
{
return false;
}
}
if (alsoCheckProperties)
{
foreach (PropertyInfo info in t.GetProperties().Where(x => x.PropertyType == typeof(TValue)))
{
if (!info.GetValue(input, null).Equals(value))
{
return false;
}
}
}
return true;
}
And your LINQ query:
var tblequipments = from d in db.tblEquipments.Include(t => t.User).Include(t => t.ChangeLog).Include(t => t.AssetType)
where CheckAllFields(d, "VALUE", true) select d;
The third parameter should be true if you want to check all fields and all properties, and false if you want to check only all fields.

Answer 3

EDIT: Someone already built this...see here.
Not a full answer, but I don't agree with assertion that you simply can't...
You could come up with an extension method that dynamically filtered the IQueryable/IEnumerable (I'm guessing IQueryable by the db variable) based on properties of a similar type for you. Here's something whipped up in Linqpad. It references PredicateBuilder and is by no means complete/fully accurate, but I tested it out in Linq-to-SQL on some of my tables and it worked as described.
void Main()
{
YourDbSet.WhereAllPropertiesOfSimilarTypeAreEqual("A String")
.Count()
.Dump();
}
public static class EntityHelperMethods
{
public static IQueryable<TEntity> WhereAllPropertiesOfSimilarTypeAreEqual<TEntity, TProperty>(this IQueryable<TEntity> query, TProperty value)
{
var param = Expression.Parameter(typeof(TEntity));
var predicate = PredicateBuilder.True<TEntity>();
foreach (var fieldName in GetEntityFieldsToCompareTo<TEntity, TProperty>())
{
var predicateToAdd = Expression.Lambda<Func<TEntity, bool>>(
Expression.Equal(
Expression.PropertyOrField(param, fieldName),
Expression.Constant(value)), param);
predicate = predicate.And(predicateToAdd);
}
return query.Where(predicate);
}
// TODO: You'll need to find out what fields are actually ones you would want to compare on.
// This might involve stripping out properties marked with [NotMapped] attributes, for
// for example.
private static IEnumerable<string> GetEntityFieldsToCompareTo<TEntity, TProperty>()
{
Type entityType = typeof(TEntity);
Type propertyType = typeof(TProperty);
var fields = entityType.GetFields()
.Where (f => f.FieldType == propertyType)
.Select (f => f.Name);
var properties = entityType.GetProperties()
.Where (p => p.PropertyType == propertyType)
.Select (p => p.Name);
return fields.Concat(properties);
}
}
Useful resources for the unresolved part:
Finding the relevant properties

Answer 4

if this help some one.
first find all properties within Customer class with same type as query:
var stringProperties = typeof(Customer).GetProperties().Where(prop =>
prop.PropertyType == query.GetType());
then find all customers from context that has at least one property with value equal to query:
context.Customer.Where(customer =>
stringProperties.Any(prop =>
prop.GetValue(customer, null) == query));