This is my transformation function call:
<p><%# MyFunctions.getDocumentCategory(Eval("DocumentID"))%></p>
This is the function:
public static string getDocumentCategory(int documentID)
{
string category;
StringBuilder sb = new StringBuilder();
// Get document categories
var ds = CategoryInfoProvider.GetDocumentCategories(documentID, "CategoryEnabled = 1", null);
// Check whether exists at least one category
if (!DataHelper.DataSourceIsEmpty(ds))
{
// Loop thru all categories
foreach (DataRow dr in ds.Tables[0].Rows)
{
sb.Append(Convert.ToString(dr["CategoryDisplayName"]) + ",");
}
}
string content = sb.ToString();
category = content.Split(',')[0];
return category;
}
}
This is the error:
MyFunctions.getDocumentCategory(int) has some invalid arguments.
I've tried an alternate form of the function that accepts strings rather than ints but it throws the same error. I've verified that the Eval("DocumentID") works correctly when placed by itself. Any ideas?
Eval returns an object. You either need to convert it to an int, or change the function to accept an object, and convert that object to an int.
<p><%# MyFunctions.getDocumentCategory( Convert.ToInt32( Eval("DocumentID") ) )%></p>
OR
public static string getDocumentCategory(object document)
{
int documentID = Convert.ToInt32( document );
etc...
}
Thanks to Doozer for the nice explanation and example.
The second approach - to accept the object and make the conversion inside your custom function - may be better to keep the transformation code cleaner. The result is equal.
Just to add a little bit - you can use Kentico's ValidationHelper for conversions, for example:
transformation:
<%# MyFunctions.getDocumentCategory(Eval("DocumentID"))%>
code:
public static string getDocumentCategory(object docID)
{
int documentID = ValidationHelper.GetInteger(docID, 0); //0 is the default value
...
Related
I'm dealing with something that seems to be a trivial task but haven't found a solution: How can I access the text on a RichSelectOneChoice? I've only found the values with richSelectOneChoice.getValue() and valueChangeEvent.getNewValue()
But, how is it possible to access the actual text?
My last attempt was this:
private RichSelectOneChoice selClaim;
public void claimTypeVCL(ValueChangeEvent ve){
Map s = selClaim.getAttributes();
Object ss = s.get(ve.getNewValue());
System.out.println(ss);
}
At the moment the console output is null for the corresponding value, no matter what the choice is.
The ADF component bound to the RichSelectOneChoice object is created as a component with inner elements.
I've also tried the solution proposed by Frank Nimphius here https://community.oracle.com/thread/1050821 with the proper object type (RichSelectOneChoice) but the if clause doesn't execute because the children are not instanceof RichSelectOneChoice as suggested but rather javax.faces.component.UISelectItem and this class doesn't include the getLabel() method and running the code actually throws a wide range of errors related either to casting an object to the target type or null pointers when trying to access the label.
Solved it using the UISelectionItem object and its getItemValue() and getItemLabel() methods instead of getLabel() or getValue(), the latter of which was available but didn't render the expected result.
The working code looks like this:
public String selectedOptionStr;
public void socClaimTypeVCL(ValueChangeEvent ve){
selectedOptionStr = "";
RichSelectOneChoice sct = (RichSelectOneChoice)ve.getSource();
List childList = sct.getChildren();
for (int i = 0; i < childList.size(); i++) {
if (childList.get(i) instanceof javax.faces.component.UISelectItem) {
javax.faces.component.UISelectItem csi = (javax.faces.component.UISelectItem) childList.get(i);
if (csi.getItemValue().toString() == ve.getNewValue().toString()) {
selectedOptionStr = csi.getItemLabel();
}
}
}
}
I have the following model:
Public Class MyModel
Public Property MyModelId As Integer
Public Property Description As String
Public Property AnotherProperty As String
End Class
Is there a method to get a property name of the Model as a string representation like the following code?
Dim propertyName as String = GetPropertyNameAsStringMethod(MyModel.Description)
So the propertyName variable has "Description" as value.
Check the Darin Dimitrov' answer on this SO thread - Reflection - get property name.
class Foo
{
public string Bar { get; set; }
}
class Program
{
static void Main()
{
var result = Get<Foo, string>(x => x.Bar);
Console.WriteLine(result);
}
static string Get<T, TResult>(Expression<Func<T, TResult>> expression)
{
var me = expression.Body as MemberExpression;
if (me != null)
{
return me.Member.Name;
}
return null;
}
}
Hope this help..
Here is a helper extension method you can use for any property:
public static class ReflectionExtensions
{
public static string PropertyName<T>(this T owner,
Expression<Func<T, object>> expression) where T : class
{
if (owner == null) throw new ArgumentNullException("owner");
var memberExpression = (MemberExpression)expression.Body;
return memberExpression.Member.Name;
}
}
However, this will only work on instances of a class. You can write a similar extension method that will operate directly on the type instead.
You need to do it using reflection.
There are already loads of posts on stack overflow like this:
How to get current property name via reflection?
Reflection - get property name
Get string name of property using reflection
Reflection - get property name
I believe that the answer will be along the lines of:
string prop = "name";
PropertyInfo pi = myObject.GetType().GetProperty(prop);
Create an extension method and then use it where needed.
Private Shared Function GetPropertyName(Of T)(exp As Expression(Of Func(Of T))) As String
Return (DirectCast(exp.Body, MemberExpression).Member).Name
End Function
have a look at this post as well.
I have solved this issue editing a bit #NiranjanKala's source example,
converting the code in vb.Net like this
<System.Runtime.CompilerServices.Extension()> _
Public Function GetPropertyName(Of T, TResult)(expression As Expression(Of Func(Of T, TResult))) As String
Dim [me] = TryCast(expression.Body, MemberExpression)
If [me] IsNot Nothing Then
Return [me].Member.Name
End If
Return Nothing
End Function
Then I am able to call the extension like this
Dim propertyName as String = GetPropertyName(Of MyModel, String)(Function(x) x.Description)
Then propertyName variable has "Description" as string value.
I need to be able to call a method and pass in an object of an unknown type
but then have the correct overload called. I also need a default implementation that accepts
object as its parameter type. What I'm seeing is that the default overload is the only one that ever gets used.
Here's the gist of what I'm trying to do:
class Formatter
{
private object Value;
public Formatter(object val){
Value = val;
}
public override string ToString()
{
return Format(Value);
}
private string Format(object value)
{
return value.ToString();
}
private string Format(DateTime value)
{
return value.ToString("yyyyMMdd");
}
}
Ok, so far so good. Now I want to be able to do this:
public static class FancyStringBuilder()
{
public static string BuildTheString()
{
var stringFormatter = new Formatter("hello world");
var dateFormatter = new Formatter(DateTime.Now);
return String.Format("{0} {1}", stringFormatter, dateFormatter);
}
}
The result of FancyStringBuilder.BuildTheString() is "hello world 2012-12-21 00:00:00.000", when I expected "hello world 20121221"
The problem is that the overload that accepts a DateTime is not being called, instead defaulting to the overload which accepts an object. How can I call the proper method without resorting to a messy switch statement?
In Formatter.ToString(), the override Formatter.Format(object) is always called. This is because the overload resolution happens at compile-time, not run-time. At compile-time, the only thing known about Value is that it's an object.
If you really want to distinguish incoming types, you'll need to do so in Formatter's constructor. In this case, rather than hanging on to the object, you could just call ToString() immediately and only store the formatted result:
class Formatter
{
string formattedValue;
public Formatter(object value)
{
formattedValue = value.ToString();
}
public Formatter(DateTime value)
{
formattedValue = value.ToString("yyyyMMdd");
}
public string ToString()
{
return formattedValue;
}
}
Note that this does assume that your object isn't changing between the time you create the Formatter object and the time Formatter.ToString() is called, or at the very least that it's okay to take a snapshot of the string representation at the time the Formatter is created.
This also assumes that you know the incoming types at compile-time. If you want a truly run-time-only solution, you'll have to use the "is" operator or a typeof() comparison.
If your goal is just to provide custom ToString() formatting based on the incoming type, I'd probably do it using a list that maps from types to format strings:
static class Formatter
{
private static List<Tuple<Type, string>> Formats;
static Formatter()
{
Formats = new List<Tuple<Type, string>>();
// Add formats from most-specific to least-specific type.
// The format string from the first type found that matches
// the incoming object (see Format()) will be used.
AddMapping(typeof(DateTime), "yyyyMMdd");
// AddMapping(typeof(...), "...");
}
private static void AddMapping(Type type, string format)
{
Formats.Add(new Tuple<Type, string>(type, format));
}
public static string Format(object value)
{
foreach (var t in Formats)
{
// If we find a type that 'value' can be assigned to
// (either the same type, a base type, or an interface),
// consider it a match, and use the format string.
if (t.Item1.IsAssignableFrom(value.GetType()))
{
return string.Format(t.Item2, value);
}
}
// If we didn't find anything, use the default ToString()...
return value.ToString();
}
}
With that, calling code then looks like:
Console.WriteLine(
"{0} {1}",
Formatter.Format(DateTime.Now),
Formatter.Format("banana"));
I think this is because the class constructor takes an object as parameter, and then assign that object to variable Value which is also an object. There for calling Format(object) since Value is of type object
Try this
public override string ToString()
{
if(Value is DateTime)
return Format(Convert.ToDateTime(Value)); //this should call the right method
return Format(Value); //works for other non-custom-format types e.g. String
}
I've seen some developers use the out keyword on parameter lists of void functions. I'm quite unclear on what the pros and cons are of code below:
List<string> listOfResult;
public void public void (out listOfResult)
{
//bla bla
}
versus
public List<string> c(out listOfResult)
{
List<string> list= new List<string>();
//bla bla
return list;
}
Are these two code snippets perfectly valid or is there any catch around the out keyword?
out keyword is handy when you need to return more than one value from function. Nice example is TryXXX methods, which return status of operation instead of throwing exceptions:
public bool TryParse(string str, out int value);
But I don't see any reason to use single out parameter with void methods... Simply return that value from your method. It will be much easier to use. Compare:
List<string> list;
GetList(out list); // confusing method name
With
List<string> list = GetList(); // nice name, one line of code
If getting of list could throw exceptions, then you can create method like this:
List<string> list;
if (TryGetList(out list)) // better than exception handling
{
// list was filled successfully
}
out parameters are quite handy when you need to return more than one value from a function.
e.g.
Return is a list of results, but you can use an out parameter to return an error message in the case when the list being returned is null.
It's a nice syntax to return multiple parameters. I personally think it's almost always better to model the return of the method as a "new object/class".
That would be:
class CResult
{
List<string> firstResult;
List<string> secondResult;
}
public CResult c()
{
// do something
return new CResult() {firstResult = ..., secondResult = ... };
}
You can see more things related to this approach here.
//out key word is used in function instead of return. we can use multiple parameters by using out key word
public void outKeyword(out string Firstname, out string SecondName)
{
Firstname = "Muhammad";
SecondName = "Ismail";
}
//on button click Event
protected void btnOutKeyword_Click(object sender, EventArgs e)
{
string first, second;
outKeyword(out first, out second);
lblOutKeyword.Text = first + " " + second;
}
Given:
public struct Id
{
readonly int m_id;
public Id(int id)
{ m_id = id; }
public static implicit operator int(Id id)
{ return id.m_id; }
public static implicit operator Id(int id)
{ return new Id(id); }
}
Can you implicitly convert an
IEnumerable<int>
to
IEnumerable<Id>
and vice versa. In some way. Note that
var ids = new int[]{ 1, 2 };
ids.Cast<Id>();
does not appear to work and covariance does not appear to be working in this case, either. Of course, doing a select will work i.e.:
ids.Select(id => new Id(id));
But I am looking for something that would make this work implicitly, so writing:
IEnumerable<Id> ids = new int[]{ 1, 2 };
And yes, I know this can be written as:
IEnumerable<Id> ids = new Id[]{ 1, 2 };
But the issue is in cases where the enumerable of ints comes from a different source, such as a file for example.
I am sorry if there already is an answer for this, but I could not find it.
According to this answer what you want is not possible. But you can get close by not implicitly casting your id but your collection. Like this :
public class Ids : List<int>
{
public static implicit operator Ids(int[] intArray)
{
var result = new Ids();
result.AddRange(intArray);
return result;
}
}
then this is possible :
Ids t = new [] { 3,4 };
What's wrong with:
IEnumerable<int> data = GetDataFromSource();
IEnumerable<Id> ids = data.select(id => new Id(id));