I would like to create a collection of key, value pairs in C# where the key is a property of an ASP.net control (e.g. ID) and the value is the value of that property. I would like to do this so I may later iterate through the collection and see if a given control has the properties in my collection (and the values of the properties in the control match the values defined in my collection). Any suggestions as to the best way to do this? Thanks for any help.
Pseudo-code example:
Properties[] = new Properties[] {new Property(){name="ID",value="TestControl1"}, new Property(){name = "Text",value="Type text here"}}
private bool controlContainsProperties(Control control){
foreach(Property Property in Properties[])
{
if((control does not contain property) || (control property value != Property.Value))
return false;
}
return true;
}
didn't test this, but here's my go:
public bool HasProperty( object target, IDictionary<string, object> values )
{
var targetType = target.GetType();
return values.All( kvp =>
{
var property = targetType.GetProperty( kvp.Key );
if ( property != null )
{
var value = property.GetValue( target, null );
if ( value != null )
return value.Equals( kvp.Value );
}
return false;
} );
}
My first idea was in using 'tag' property, but then I realized that there are no tags in APS.NET controls. However, there is an answered question about tags.
In the same thread there is a solution with 'Attributes' property map - looks promising.
Related
I have a Category entity which has a Nullable ParentId field. When the method below is executing and the categoryId is null, the result seems null however there are categories which has null ParentId value.
What is the problem in here, what am I missing?
public IEnumerable<ICategory> GetSubCategories(long? categoryId)
{
var subCategories = this.Repository.Categories.Where(c => c.ParentId == categoryId)
.ToList().Cast<ICategory>();
return subCategories;
}
By the way, when I change the condition to (c.ParentId == null), result seems normal.
Other way:
Where object.Equals(c.ParentId, categoryId)
or
Where (categoryId == null ? c.ParentId == null : c.ParentId == categoryId)
The first thing to do is to put on logging, to see what TSQL was generated; for example:
ctx.Log = Console.Out;
LINQ-to-SQL seems to treat nulls a little inconsistently (depending on literal vs value):
using(var ctx = new DataClasses2DataContext())
{
ctx.Log = Console.Out;
int? mgr = (int?)null; // redundant int? for comparison...
// 23 rows:
var bosses1 = ctx.Employees.Where(x => x.ReportsTo == (int?)null).ToList();
// 0 rows:
var bosses2 = ctx.Employees.Where(x => x.ReportsTo == mgr).ToList();
}
So all I can suggest is use the top form with nulls!
i.e.
Expression<Func<Category,bool>> predicate;
if(categoryId == null) {
predicate = c=>c.ParentId == null;
} else {
predicate = c=>c.ParentId == categoryId;
}
var subCategories = this.Repository.Categories
.Where(predicate).ToList().Cast<ICategory>();
Update - I got it working "properly" using a custom Expression:
static void Main()
{
ShowEmps(29); // 4 rows
ShowEmps(null); // 23 rows
}
static void ShowEmps(int? manager)
{
using (var ctx = new DataClasses2DataContext())
{
ctx.Log = Console.Out;
var emps = ctx.Employees.Where(x => x.ReportsTo, manager).ToList();
Console.WriteLine(emps.Count);
}
}
static IQueryable<T> Where<T, TValue>(
this IQueryable<T> source,
Expression<Func<T, TValue?>> selector,
TValue? value) where TValue : struct
{
var param = Expression.Parameter(typeof (T), "x");
var member = Expression.Invoke(selector, param);
var body = Expression.Equal(
member, Expression.Constant(value, typeof (TValue?)));
var lambda = Expression.Lambda<Func<T,bool>>(body, param);
return source.Where(lambda);
}
My guess is that it's due to a rather common attribute of DBMS's - Just because two things are both null does not mean they are equal.
To elaborate a bit, try executing these two queries:
SELECT * FROM TABLE WHERE field = NULL
SELECT * FROM TABLE WHERE field IS NULL
The reason for the "IS NULL" construct is that in the DBMS world, NULL != NULL since the meaning of NULL is that the value is undefined. Since NULL means undefined, you can't say that two null values are equal, since by definition you don't know what they are.
When you explicitly check for "field == NULL", LINQ probably converts that to "field IS NULL". But when you use a variable, I'm guessing that LINQ doesn't automatically do that conversion.
Here's an MSDN forum post with more info about this issue.
Looks like a good "cheat" is to change your lambda to look like this:
c => c.ParentId.Equals(categoryId)
You need to use operator Equals:
var subCategories = this.Repository.Categories.Where(c => c.ParentId.Equals(categoryId))
.ToList().Cast<ICategory>();
Equals fot nullable types returns true if:
The HasValue property is false, and the other parameter is null. That is, two null values are equal by definition.
The HasValue property is true, and the value returned by the Value property is equal to the other parameter.
and returns false if:
The HasValue property for the current Nullable structure is true, and the other parameter is null.
The HasValue property for the current Nullable structure is false, and the other parameter is not null.
The HasValue property for the current Nullable structure is true, and the value returned by the Value property is not equal to the other parameter.
More info here Nullable<.T>.Equals Method
Or you can simply use this. It will also translate to a nicer sql query
Where((!categoryId.hasValue && !c.ParentId.HasValue) || c.ParentId == categoryId)
What about something simpler like this?
public IEnumerable<ICategory> GetSubCategories(long? categoryId)
{
var subCategories = this.Repository.Categories.Where(c => (!categoryId.HasValue && c.ParentId == null) || c.ParentId == categoryId)
.ToList().Cast<ICategory>();
return subCategories;
}
Linq to Entities supports Null Coelescing (??) so just convert the null on the fly to a default value.
Where(c => c.ParentId == categoryId ?? 0)
Given is a Workflow Foundation 4 runtime that is working against a website ;)
We need to get the arguments of workflows to show the user an editor to enter the arguments. For that we need all arguments with names, types and - default values, as well as an indication whether an argument is required.
Workflows are stored as XAML files.
How to do that? The data seems to be in the Activity Metadata which seems to be not avaialble outside the Workflow. In addition, the Workflow Engine ModelService is for the Designer and has a lot of overhead.
Any easy way to retrieve this information?
I've already done something similar. Reflection might be your best (and only) option if you want a generic approach.
// Just an holder for InArgument informations
class InArgumentInfo
{
public string InArgumentName { get; set; }
public string InArgumentDescription { get; set; }
public bool InArgumentIsRequired { get; set; }
}
static ICollection<InArgumentInfo> GetInArgumentsInfos(Activity activity)
{
var properties = activity.GetType()
.GetProperties()
.Where(p => typeof(InArgument).IsAssignableFrom(p.PropertyType))
.ToList();
var argumentsCollection = new Collection<InArgumentInfo>();
foreach (var property in properties)
{
var descAttribute = property
.GetCustomAttributes(false)
.OfType<DescriptionAttribute>()
.FirstOrDefault();
string description = descAttribute != null && !string.IsNullOrEmpty(descAttribute.Description) ?
descAttribute.Description :
string.Empty;
bool isRequired = property
.GetCustomAttributes(false)
.OfType<RequiredArgumentAttribute>()
.Any();
argumentsCollection.Add(new InArgumentInfo
{
InArgumentName = property.Name,
InArgumentDescription = description,
InArgumentIsRequired = isRequired
});
}
return argumentsCollection;
}
This way you can not only retrieve the argument's name but also other information hold by the argument's attributes. For example I choose to give argument an user-friendly name through [Description] attribute (eg. instead of MyPropertyName user sees "My Property Name").
Note: if you can ensure that you activity is an ActivityBuilder or DynamicActivity they both have Properties property that you can use, but the principle is the same.
Load it as DynamicActivity and iterate over Properties property
var dynamicActivity = ActivityXamlServices.Load(foo) as DynamicActivity
foreach(DynamicActivityProperty prop in dynamicActivity.Properties)
{
// ...
}
UPDATE: Missed default value part
foreach (var prop in dynamicActivity .Properties)
{
object defaultValue;
if (prop.Value == null)
{
defaultValue = null;
}
else
{
Type genericTypeDefinition = prop.Type.GetGenericTypeDefinition();
if (genericTypeDefinition == typeof(InArgument<>) || genericTypeDefinition == typeof(InOutArgument<>))
{
var valueProp = prop.Value.GetType().GetProperty("Expression", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.DeclaredOnly);
var expression = valueProp.GetValue(prop.Value, null);
var expressionValueProp = expression.GetType().GetProperty("Value");
defaultValue = expressionValueProp.GetValue(expression, null);
}
}
}
Not totally guaranteed, there are some checks you have to do.
I have following Linq query/function in my MVC3 application.
public AuditTrail GetNamesAddressesEmployers(long registryId , int changedField) {
var otherNameAndAddress = (from a in context.AuditTrails
where a.ChangedField == changedField
&& a.RegistryId == registryId
select a).FirstOrDefault();
return otherNameAndAddress;
}
I want that if otherNameAndAddress = null then its properties should be assigned some values.
otherNameAndAddress has Name and description property. This GetNamesAddressesEmployers is being used at 3 places. I want to assign different values to name and description when otherNameAndAddress = null at all three locations.
You're already using FirstOrDefault() so why not specify the Default:
public AuditTrail GetNamesAddressesEmployers(long registryId, int changedField)
{
return context.AuditTrails
.Where(a => a.ChangedField == changedField
&& a.RegistryId == registryId)
.DefaultIfEmpty(new AuditTrail { /* fill properties here */ })
.FirstOrDefault();
}
Well, you could change the return statement to:
return otherNameAndAddress ?? new AuditTrail { Name = "Default",
Description = "Default };
or something like that... but you say you want to assign different default values for different calls. That means you'll either need to pass the default in, or perform the defaulting (e.g. in the same way, via the null-coalescing operator) at the call site.
For example:
public AuditTrail GetNamesAddressesEmployers(long registryId, int changedField,
AuditField defaultValue) {
var otherNameAndAddress = (from a in context.AuditTrails
where a.ChangedField == changedField
&& a.RegistryId == registryId
select a).FirstOrDefault();
return otherNameAndAddress && defaultValue;
}
or keep it as it currently is, and use this at the call site:
var auditTrail = GetNamesAddressesEmployers(registryId, changedField) ??
new AuditTrail { Name = "Foo", Description = "Bar" };
It's not really clear which is best based on your description.
EDIT: As mentioned by Justin, you could use DefaultIfEmpty instead (just before FirstOrDefault). That means you have to pass the value in rather than doing it at the call site, but other than that they're very similar solutions.
We wanted to assign/add an item to a Dictionary using the key index, like this:
Dictionary<string, object> dict = new Dictionary<string, object>();
dict["key"] = dict["key"] ?? "object";
But it results to: "The given key was not present in the dictionary."
Is there any way we could assign values to this dictionary the same as the way I assign values to sessions, using null coalesce:
Session["Member"] = Session["Member"] ?? new Member();
Thanks
Edit:
I actually tried to override the indexer from a child class of dictionary, but to no avail.
Implementing IDictionary interface would seem too much because we just need the functionality of the code below (i.e., return null if key is not found).
So I think, maybe we could use extensions like:
public static TValue [this Dictionary<TKey, TValue> thisDictionary, TKey key] {
get { return thisDictionary.ContainsKey(key) ? thisDictionary[key] : null; }
set { thisDictionary[key] = value; }
}
but it is not working or even compiling.
Any other simpler ways so we could reuse this indexer functionality? Thanks a lot.
If you want to do this inline:
dict["key"] = dict.ContainsKey("key") ? (dict["key"] ?? "object") : "object";
Alternatively:
dict["key"] = dict.ContainsKey("key") && dict["key"] == null ? dict["key"] : "object";
Edit as per comments:
public static TValue GetSafe(this Dictionary<TKey, TValue> thisDictionary, TKey key)
{
if (!thisDictionary.ContainsKey(key))
thisDictionary[key] = null;
return thisDictionary[key];
}
This allows you to do this:
thisDictionary["randomKey"] = thisDictionary.GetSafe("randomKey") ?? "someValue";
As you noted, trying to fetch a missing key throws an exception. You have to check if the key exists first:
if( !Session.ContainsKey("Member") )
Session["Member"] = new Member();
Edit:
And to answer your question; you can create your own indexer or implement the IDictionary interface. This way you can avoid the default behavior of throwing an exception
OK, I am sorting an XMLListCollection in alphabetical order. I have one issue though. If the value is "ALL" I want it to be first in the list. In most cases this happens already but values that are numbers are being sorted before "ALL". I want "ALL" to always be the first selection in my dataProvider and then the rest alphabetical.
So I am trying to write my own sort function. Is there a way I can check if one of the values is all, and if not tell it to do the regular compare on the values?
Here is what I have:
function myCompare(a:Object, b:Object, fields:Array = null):int
{
if(String(a).toLowerCase() == 'all')
{
return -1;
}
else
if(String(b).toLowerCase() == 'all')
{
return 1;
}
// NEED to return default comparison results here?
}
//------------------------------
var sort:Sort = new Sort();
sort.compareFunction = myCompare;
Is there a solution for what I am trying to do?
The solution from John Isaacks is awesome, but he forgot about "fields" variable and his example doesn't work for more complicated objects (other than Strings)
Example:
// collection with custom objects. We want to sort them on "value" property
// var item:CustomObject = new CustomObject();
// item.name = 'Test';
// item.value = 'Simple Value';
var collection:ArrayCollection = new ArrayCollection();
var s:Sort = new Sort();
s.fields = [new SortField("value")];
s.compareFunction = myCompare;
collection.sort = s;
collection.refresh();
private function myCompare(a:Object, b:Object, fields:Array = null):int
{
if(String((a as CustomObject).value).toLowerCase() == 'all')
{
return -1;
}
else if(String((b as CustomObject).value).toLowerCase() == 'all')
{
return 1;
}
// NEED to return default comparison results here?
var s:Sort = new Sort();
s.fields = fields;
var f:Function = s.compareFunction;
return f.call(null,a,b,fields);
}
Well I tried something out, and I am really surprised it actually worked, but here is what I did.
The Sort class has a private function called internalCompare. Since it is private you cannot call it. BUT there is a getter function called compareFunction, and if no compare function is defined it returns a reference to the internalCompare function. So what I did was get this reference and then call it.
private function myCompare(a:Object, b:Object, fields:Array = null):int
{
if(String(a).toLowerCase() == 'all')
{
return -1;
}
else if(String(b).toLowerCase() == 'all')
{
return 1;
}
// NEED to return default comparison results here?
var s:Sort = new Sort();
var f:Function = s.compareFunction;
return f.call(null,a,b,fields);
}
Thanks guys, this helped a lot. In our case, we needed all empty rows (in a DataGrid) on the bottom. All non-empty rows should be sorted normally. Our row data is all dynamic Objects (converted from JSON) -- the call to ValidationHelper.hasData() simply checks if the row is empty. For some reason the fields sometimes contain the dataField String value instead of SortFields, hence the check before setting the 'fields' property:
private function compareEmptyAlwaysLast(a:Object, b:Object, fields:Array = null):int {
var result:int;
if (!ValidationHelper.hasData(a)) {
result = 1;
} else if (!ValidationHelper.hasData(b)) {
result = -1;
} else {
if (fields && fields.length > 0 && fields[0] is SortField) {
STATIC_SORT.fields = fields;
}
var f:Function = STATIC_SORT.compareFunction;
result = f.call(null,a,b,fields);
}
return result;
}
I didn't find these approaches to work for my situation, which was to alphabetize a list of Strings and then append a 'Create new...' item at the end of the list.
The way I handled things is a little inelegant, but reliable.
I sorted my ArrayCollection of Strings, called orgNameList, with an alpha sort, like so:
var alphaSort:Sort = new Sort();
alphaSort.fields = [new SortField(null, true)];
orgNameList.sort = alphaSort;
orgNameList.refresh();
Then I copied the elements of the sorted list into a new ArrayCollection, called customerDataList. The result being that the new ArrayCollection of elements are in alphabetical order, but are not under the influence of a Sort object. So, adding a new element will add it to the end of the ArrayCollection. Likewise, adding an item to a particular index in the ArrayCollection will also work as expected.
for each(var org:String in orgNameList)
{
customerDataList.addItem(org);
}
Then I just tacked on the 'Create new...' item, like this:
if(userIsAllowedToCreateNewCustomer)
{
customerDataList.addItem(CREATE_NEW);
customerDataList.refresh();
}