Questions tagged [out-parameters]
145 questions
130
votes
10 answers
Why doesn't 'ref' and 'out' support polymorphism?
Take the following:
class A {}
class B : A {}
class C
{
C()
{
var b = new B();
Foo(b);
Foo2(ref b); // <= compile-time error:
// "The 'ref' argument doesn't match the parameter type"
}
…
Andreas Grech
- 105,982
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108
votes
7 answers
Is there a VB.NET equivalent of C# out parameters?
Does VB.NET have a direct equivalent to C# out function parameters, where the variable passed into a function does not need to be initialised?
cspolton
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89
votes
2 answers
Passing a property as an 'out' parameter in C#
Suppose I have:
public class Bob
{
public int Value { get; set; }
}
I want to pass the Value member as an out parameter like
Int32.TryParse("123", out bob.Value);
but I get a compilation error, "'out' argument is not classified as a variable."…
thorncp
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48
votes
2 answers
How can I invoke a method with an out parameter?
I want expose WebClient.DownloadDataInternal method like below:
[ComVisible(true)]
public class MyWebClient : WebClient
{
private MethodInfo _DownloadDataInternal;
public MyWebClient()
{
_DownloadDataInternal =…
ldp615
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- 13
45
votes
10 answers
How best to implement out params in JavaScript?
I'm using Javascript with jQuery. I'd like to implement out params. In C#, it would look something like this:
/*
* odp the object to test
* error a string that will be filled with the error message if odp is illegal. Undefined otherwise.
…
Nick Heiner
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41
votes
3 answers
Is there a way to omit out parameter?
Let's assume I have a function with out parameter, however I do not need its value. Is there a way to pass no actual parameter if given result will be thrown away anyway?
EDIT:
Although the question has been voted to be dupe of Optional Output…
konrad.kruczynski
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19
votes
2 answers
passing out parameter
I wrote a method with an out parameter:
-(NSString *)messageDecryption:(NSString *)receivedMessage outParam:(out)messageCondent
{
messageCondent = [receivedMessage substringFromIndex:2];
return [receivedMessage…
Vipin
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19
votes
6 answers
Null out parameters in C#?
After reading on stackoverflow that in the case of checking the format of a DateTime you should use DateTime.TryParse. After trying some regex expressions they seem to get long and nasty looking to cover lots of the formatting.
But TryParse requires…
chobo2
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18
votes
2 answers
Fetch Oracle table type from stored procedure using JDBC
I'm trying to understand different ways of getting table data from Oracle stored procedures / functions using JDBC. The six ways are the following ones:
procedure returning a schema-level table type as an OUT parameter
procedure returning a…
Lukas Eder
- 211,314
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- 689
- 1,509
18
votes
8 answers
Real-world examples where C# 'out' parameters are useful?
I'm reading up on core C# programming constructs and having a hard time wrapping my head around the out parameter modifier. I know what it does by reading but am trying to think of a scenerio when I would use it.
Can someone give me a real-world…
clickatwill
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18
votes
6 answers
In what situations are 'out' parameters useful (where 'ref' couldn't be used instead)?
As far as I can tell, the only use for out parameters is that a caller can obtain multiple return values from a single method invocation. But we can also obtain multiple result values using ref parameters instead!
So are there other situations where…
flockofcode
- 1,799
- 2
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17
votes
2 answers
How to pass 'out' parameter into lambda expression
I have a method with the following signature:
private PropertyInfo getPropertyForDBField(string dbField, out string prettyName)
In it, I find the associated value prettyName based on the given dbField. I then want to find all properties, if any,…
Sarah Vessels
- 30,930
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16
votes
3 answers
Out parameters in C
void swap(int &first, int &second){
int temp = first;
first = second;
second = temp;
}
int a=3,b=2;
swap(a,b);
The compiler complaints that void swap(int &first, int &second) has a syntax error. Why? Doesn't C support references?
user1128265
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16
votes
2 answers
Why don't anonymous delegates/lambdas infer types on out/ref parameters?
Several C# questions on StackOverflow ask how to make anonymous delegates/lambdas with out or ref parameters. See, for example:
Calling a method with ref or out parameters from an anonymous method
Write a lambda or anonymous function that accepts…
John Feminella
- 303,634
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15
votes
4 answers
Why is an out parameter not allowed within an anonymous method?
This is not a dupe of Calling a method with ref or out parameters from an anonymous method
I am wondering why out parameters are not allowed within anonymous methods. Not allowing ref parameters makes a bit more sense to me, but the out parameters,…
Chris Ballance
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