Error 1 Use Of Unassigned Local Variable Struct
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Use Of Unassigned Local Variable C# Struct
hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges error cs0165 use of unassigned local variable Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. use of unassigned local variable unity Join them; it only takes a minute: Sign up C# Structs: Unassigned local variable? up vote 15 down vote favorite 3 From the documentation: Unlike classes, structs can be instantiated without using a new operator. So why am
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I getting this error: Use of unassigned local variable 'x' When I try to do this? Vec2 x; x.X = det * (a22 * b.X - a12 * b.Y); x.Y = det * (a11 * b.Y - a21 * b.X); Where Vec2 x is a struct? c# struct share|improve this question asked Jan 15 '10 at 4:02 mpen 85.8k123491748 add a comment| 2 Answers 2 active oldest votes up vote 17 down vote accepted Well, are X and
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Y properties (rather than fields)? If so, that's the problem. Until all the fields within x are definitely assigned, you can't call any methods or properties. For instance: public struct Foo { public int x; public int X { get { return x; } set { x = value; } } } class Program { static void Main(string[] args) { Foo a; a.x = 10; // Valid Foo b; b.X = 10; // Invalid } } Is Vec2 your own type? Do you have access to the fields involved, or only the properties? If it's your own type, I would strongly urge you to try to stick to immutable structs. I know managed DirectX has some mutable structs for getting as close to optimal performance as possible, but that's at the cost of strange situations like this - and much worse, to be honest. I would personally give the struct a constructor taking X and Y: Vec2 x = new Vec2(det * (a22 * b.X - a12 * b.Y), det * (a11 * b.Y - a21 * b.X)); share|improve this answer answered Jan 15 '10 at 4:07 Jon Skeet 899k48665207455 Ah, they were properties. Good catch! I'll consider making X and Y private if I can get away with it. –mpen Jan 15 '10 at 4:23 2 +1. Nice one, Jon. –Mitch Wheat Jan 15 '10 at 4:49
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Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only use of unassigned local variable c# for loop takes a minute: Sign up Why compile error “Use of unassigned local variable”? up vote 27 down vote favorite 5 My code is the following int tmpCnt; if (name == "Dude") tmpCnt++; Why is there an error Use of unassigned http://stackoverflow.com/questions/2069435/c-sharp-structs-unassigned-local-variable local variable tmpCnt? I know I didn't explicitly initialize it but due to Default Value Table a value type is initialized with 0 anyways. The reference also reminds me: Remember that using uninitialized variables in C# is not allowed. But why do I have to do it explicitly if it's already done by default? Wouldn't it gain performance if I wouldn't have to do it? Just wondering... c# .net compiler-construction share|improve this question asked Feb 10 '12 at 18:41 theknut http://stackoverflow.com/questions/9233000/why-compile-error-use-of-unassigned-local-variable 59521231 Can anyone help me with the headline? Couldn't find a fitting for this one :-S –theknut Feb 10 '12 at 18:44 I have a local struct, never initialized, compiles with no errors. Today I created a different struct, treated identically, got "uninitialized local variable error". All its members were set to a value before use, but I could not first set it to null, since it was 'just' a struct. The struct that compiled contained only ints, bools and strings. The one that gave the error also contained DateTimes. "MyStructType myStruct = new MyStructType();" killed the error. Not the first time I've been bitten by missing something a few levels down. –mickeyf Jun 2 at 19:14 add a comment| 9 Answers 9 active oldest votes up vote 55 down vote accepted Local variables aren't initialized. You have to manually initialize them. Members are initialized, for example: public class X { private int _tmpCnt; // This WILL initialize to zero ... } But local variables are not: public static void SomeMethod() { int tmpCnt; // This is not initialized and must be assigned before used. ... } So your code must be: int tmpCnt = 0; if (name == "Dude") tmpCnt++; So the long and the short of it is, members are initialized, locals are not. That is why you get the compiler error. share|improve this answer answered Feb 10 '12 at 18:45 James Michael H
C# Handling non assigned struct objects in C# If you have ever used structs and haduse of unassigned local variable errors from your editor i.e Visual Studio then there is a simple solution. The problem comes about because the compiler is not clever http://blog.strictly-software.com/2013/05/handling-unassigned-local-variable.html enough to realise that the struct object will always be initialised when used. This is usually because the struct object isinitialisedwithin an IF statementor other code branch which makes the compiler believe that a similar situation to the"unreachable code"error has https://github.com/dotnet/roslyn/issues/1722 been detected. As the compile cannotdefinitelytell that thestructobject will always be initialised when it gets used it will raise a compile error. In Visual Studio it will usually show up with a red line under the code in question with use of the error message "use of unassigned local variable ..." Here is a simple example where the struct object is populated with a method and starts off in the main constructor method unassigned. However because of the nature of the code and the fact that on the first loop iteration oldID will never be the same as currentID (as oldID starts off as 0 and currentID as 1) then the IF statement will always cause the this.FillObject method to run on use of unassigned each iteration. Therefore the myvar variable which is based on a struct called myStructObj will always get populated with new values from the loop. However the compiler cannot tell this from the code and will raise the"use of unassigned local variable myvar" error when I try to pass the object as a parameter into the this.OutputObject(myvar) method which just outputs the current property values from the object. public class Test { /* example of a method that believes the struct object won't get assigned even though due to the if statement it always will */ public void Test() { myStructObj myvar; int oldID = 0; /* just a basic loop from 1 to 9 */ for(int currentID = 1; currentID < 10; currentID++) { /* as the oldID starts as 0 and currentID starts as 1 on the first loop iteration we will always populate the struct object with values */ if(oldID != currentID) { /* populate our struct object using our FillObject method */ myvar = this.FillObject(currentID, "ID: " + currentID.ToString()); oldID = currentID; } /* try and parse our struct to a method to output the values - this is where we would get our red line under the myvar parameter being passed into the OutputObject method e.g. "use of unassigned local variable myvar" */ this.OutputObject(myvar); } } /* Simple method to output the properties of the object to the console */ pr
Sign in Pricing Blog Support Search GitHub This repository Watch 890 Star 6,340 Fork 1,521 dotnet/roslyn Code Issues 3,201 Pull requests 128 Projects 0 Wiki Pulse Graphs New issue 'error CS0165: Use of unassigned local variable' is not produced for structs with a private reference type field from a different assembly #1722 Closed hmemcpy opened this Issue Apr 1, 2015 · 6 comments Projects None yet Labels Area-Compilers Bug Language-C# Resolution-By Design Verified Milestone 1.0 (stable) Assignees No one assigned 4 participants hmemcpy commented Apr 1, 2015 Here's a minimal repro: ClassLibrary1: MyStruct.cs using System; namespace ClassLibrary1 { public struct MyStruct { private readonly object a; } } ConsoleApplication1: Program.cs using System; using ClassLibrary1; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { MyStruct mystruct; Console.WriteLine(mystruct); // <--MISSING: error CS0165 does not happen, project compiles in VS2015 CTP6. } } } In both VS2012 and VS2013 this produces an error, as expected. In VS2015 CTP6 this compiles successfully. A struct with a private reference type field will not cause the compilation to fail. Changing to a value type, or making the field public will cause the error, as expected. Also, if the struct is defined in the same assembly, it will fail, as expected. hmemcpy changed the title from 'error CS0165: Use of unassigned local variable' is not generated for structs with a private reference type field from a different assembly to 'error CS0165: Use of unassigned local variable' is not produced for structs with a private reference type field from a different assembly Apr 1, 2015 hmemcpy commented Apr 1, 2015 Just tried it with /features:strict, and it gives an error, as wit