How to get an entire struct out of a class?

doug 0

Hi Simon & Mykonian Here is some code to help shed some light on my issue. It appears I can access the struct but all their values are zero when I access them from Cross.Process so I assumed I was trying to improperly access them. Any ideas? class Form1() { public struct crossvars { public uint bases; public double step; public double baselo; public double basehi; public byte SLOPE; }crossvars myCrossVars; public crossvars GetBasehi { get { return myCrossVars; } set { } } void someMethod() { Cross myCrossObj = new Cross(); Console.WriteLine("basehi_before_passingto_CROSS={0}", myCrossVars.basehi); myCrossObj.Process(LeftWheel, MinSampleSize, FileCount, steps); Console.WriteLine("basehi_backfrom_passingto_CROSS={0}", myCrossVars.basehi); } } class Cross() { void Process() { //try to create obj and access struct thru property Get Form1 myStructObj = new Form1(); Console.WriteLine("basehi_in Cross.Process_Get={0}",myStructObj.GetBasehi.basehi); //try another way to access the struct create obj for struct itself Form1.crossvars myObj = new Form1.crossvars(); Console.WriteLine("basehi_in Cross.Process_structobject={0}",myObj.basehi); } } The struct member myCrossVars.basehi is being set thru a updn control in Form1. The following output resulted (Form1) basehi_before_passingto_CROSS=32.9 (Cross) basehi_in Cross.Process_Get=0 (Cross) basehi_in Cross.Process_structobject=0 (Form1)basehi_backfrom_passingto_CROSS=32.9 end output As you can see the value being returned for basehi from Form1 class is 0(zero) yet the value is correct before and after passing to Cross.Process. I can't get the correct values when attempting to access the struct from the Cross class. The accessibility is set to public on the struct decleration, the propety and members. Any ideas? Thank you db

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bilnaad21y ago
I believe you have two options here. I was looking for a solution a while ago myself to keep variable data alive (out of it's scope). The namespace to use: using System.Runtime.InteropServices; 1. The marshal class. This class has several functions to write/read data to/from unmanaged memory. Because this memory is outside of the GarbageCollector's reach it will not be destroyed by default. You have to do that yourself. 2. The GCHandle. The GCHandle is an handle to the data for the GC to use. Also this data is not freed automaticly. You have to free the data with a function within this struct. Try these two options and let me know when you get into trouble. I hope this helps :)
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doug 022y ago
I agree with you 100%, no matter what you initialize it to whether it's all 5's or all 10's, I get back what I initialize it to. In the above case (my code) you are correct, the default value is going to be zero and in your example it will be 5. My problem is that the only way to access the struct in the main thread is to create an object in the Cross class, which forces me (at a minimum) to call the default constructor as indicated above. This however initializes all the member variables essentially erasing the last value that the updn control updated the struct with. What I really want is to get that last known value of basehi from the struct, but because Process() is in a different class than that of which the struct was declared, the constructor is reinitalizing all members. If this were ANSI C, it would be like this... 1.You have a main loop that the user updates a member variable BASEHI of struct crossvars 2.You call a module called Cross and execute Process() which exists within the module. 3.Process() requires the last known value a member variable BASEHI to do its calculations. Becasue BASEHI exists in the main thread or main module and we want access to the crossvars struct, we have to declare the struct a global variable and declare it an extern variable which is linked in a header file. I am essentially trying to do the same thing in VC#. I have to be missing a concept here about namespaces or something. How do I keep the struct crossvars "alive" so that once I have passed control to anther class I can still access the members of that struct, it's in the main thread so it isn't destroyed once I call a method in another class is it???? Thanks db
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bilnaad22y ago
Try this: public void myCrossMethod { //THIS IS WHERE I AM TRYING TO ACCESS THE STRUCT IN FORM1 Form1.crossvars myCrossVars = new Form1.crossvars(5,5,5,5,5,5,5,5); Console.WriteLine("***Basehi={0}",myCrossVars.basehi); //I GET ZERO FOR THE MEMBER } You did not initialize the struct using it's proper constructor. So it's obvious the fields holds their default values.
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doug 022y ago
Hi, I noticed that your struct declaration was outside the ConsoleStart class, my declaration is below...question to follow... namespace mynamespace { class Form1() //THIS IS THE MAIN THREAD { private void updnHPF_ValueChanged(object sender, System.EventArgs e) { myCrossVars.basehi = (double)updnHPF.Value; } public struct crossvars { public double bases; public double step; public double baselo; public double basehi; public byte SLOPE; public byte IRI; public byte RN; public byte BWF; public crossvars(double bases,double step,double baselo,double basehi,byte SLOPE,byte IRI,byte RN,byte BWF) { this.basehi =basehi; this.baselo =baselo; this.BWF = BWF; this.bases=bases; this.step=step; this.SLOPE=SLOPE; this.IRI=IRI; this.RN=RN; //Console.WriteLine("INCONSTR basehi={0}",basehi); } public double GetBasehiInCrossVars { get { return (basehi); } set { } } } crossvars myCrossVars; }//end class }//end namespace namespace mynamespace { public class Cross { public void myCrossMethod { //THIS IS WHERE I AM TRYING TO ACCESS THE STRUCT IN FORM1 Form1.crossvars myCrossVars = new Form1.crossvars(); Console.WriteLine("***Basehi={0}",myCrossVars.basehi); //I GET ZERO FOR THE MEMBER } } } Could it be that I cannot retrieve the correct value from Form1 (main thread) because the struct is within that class and not the namespace. Furthermore, how are you to retrieve the last value the updown control returned if when you create a new object in the Cross class to go get it that the constructor resets all the member values.
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bilnaad22y ago
I tested your struct with this code. And it works fine :) using System; namespace DevConsole { public struct crossvars { public double bases; public double step; public double baselo; public double basehi; public byte SLOPE; public byte IRI; public byte RN; public byte BWF; public crossvars(double bases,double step,double baselo,double basehi,byte SLOPE,byte IRI,byte RN,byte BWF) { this.basehi =basehi; this.baselo =baselo; this.BWF = BWF; this.bases=bases; this.step=step; this.SLOPE=SLOPE; this.IRI=IRI; this.RN=RN; } public override string ToString() { return string.Format( "bases={0}\nstep={1}\nbaselo={2}\nbasehi={3}\nSLOPE={4}\nIRI={5}\nRN={6}\nBWF={7}\n", bases ,step ,baselo ,basehi ,SLOPE ,IRI ,RN, BWF ); } } class ConsoleStart { [STAThread] static void Main(string[] args) { crossvars vars = new crossvars(0.1, 1.2 ,2.3 ,3.4 ,0 ,0 ,0 ,255); Console.WriteLine(vars); Console.Read(); } } } Also I couldn't really understand your code. You wrote this code: crossvars vars= new crossvars(0,0.1,0,222,0,0,0,0); //declare new obj initialize Console.WriteLine("INFORM1_CONST basehi={0}",myCrossVars.basehi); You initialize a new crossvar varaible named vars. Since this object is initialized I would suspect that you use that object. But you don't. You used the uninitialized field from the class. That doesn't make any sense and I think that's your problem.
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doug 022y ago
Hi, I have added the following constructor to the struct. public struct crossvars { public double bases; public double step; public double baselo; public double basehi; public byte SLOPE; public byte IRI; public byte RN; public byte BWF; public crossvars(double bases,double step,double baselo,double basehi,byte SLOPE,byte IRI,byte RN,byte BWF) { this.basehi =basehi; this.baselo =baselo; this.BWF = BWF; this.bases=bases; this.step=step; this.SLOPE=SLOPE; this.IRI=IRI; this.RN=RN; Console.WriteLine("INCONSTR basehi={0}",basehi); } public double GetBasehiInCrossVars { get { return (basehi); } set { } } } crossvars myCrossVars; I initialize the struct via the following line in the Form1 constructor.. Basehi =222 which I pass Form1() //form1 constructor { crossvars vars= new crossvars(0,0.1,0,222,0,0,0,0); //declare new obj initialize Console.WriteLine("INFORM1_CONST basehi={0}",myCrossVars.basehi); } I am still not getting the correct values outside the constructor, it is like the members get reinitialized to zero after the struct constructor. output is below INCONSTR basehi=222 //print out value in struct constructor INFORM1_CONST basehi=0 IN_CROSS.Process_Basehi=0 //this is value I get when trying to access from Cross class Any more ideas? Thanks db
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bilnaad22y ago
As I read through the code I didn't see any initialisation of the crossvars fields. If you have a struct without an constructor that inits every field every fields will be initialised to it's default value.
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