Property or indexer cannot be assigned to "--" it is read only

Question

1.00/5 (2 votes)

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I have the following code

C#

private readonly string _cstrvalueMember;    //Holds value
private readonly string _cstrdisplayMember;

object obj;
LookupDTO lkpDTOo =(LookupDTO) obj;
if (lkpDTOo.strValueMember == "3")
{
    lkpDTOo.strDisplayMember = "--";
}

But lkpDTOo.strDisplayMember = "--"; here I am getting error like

VB

Error   50  Property or indexer 'XXX.DTO.LookupDTO.strDisplayMember' cannot be assigned to -- it is read only

Even though I removed readonly and made it public it is not working

Posted 14-Jul-14 3:00am

chandra sekhar

Updated 16-Jul-14 6:38am

Chris Maunder772.9K

v4

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johannesnestler 14-Jul-14 9:07am

Yes so what's the question? You should know variable scope and access rules, otherwise asking QA makes not much sense. You didn't show your actual code, so I see no reason to guess what could be your problem. Show actual, relevant code and ask again(?) - Btw. Access such information with Properties (get/set) and not through variables (I think that is OOP lesson1)

chandra sekhar 14-Jul-14 9:09am

But how can i access that member? I have shown on which i am working :|

johannesnestler 14-Jul-14 9:28am

Others answered it in between. But I'm puzzled: You make a variable "readonly", next you provide a thing called "get". Then you aks "why can't I set it", You didn't mention any properies first, just that you made the variable public (this can't be true because it would have worked). So even if you are a beginner you should have asked what "readonly and get" means - C# is a language you can read like spoken langauage. So realy spend ONE day (should be enough) to go through the c# basics (again)..

Kornfeld Eliyahu Peter 14-Jul-14 9:39am

See his post on one of the solutions...
He thinks CP is a compiler service, so feed us line-by-line :-)

Sergey Alexandrovich Kryukov 14-Jul-14 11:36am

The whole idea to assign hard-coded immediate constant "--" in code is quite bad. You did not explain to us the goal of it. Anyway, here is how it looks: you specifically created a read-only member yourself and trying to assign a value to it. Your intention is hard to understand. Your already got technical advice in other solution, but I'm not sure they will solve your problem, which is just understanding of programming. You should understand every line you write.

—SA

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CHill60 · Answer 1 · 2014-07-14T03:14:00

You have not defined the setter for strDisplayMember in your class.

Try

C#

public string strDisplayMember
{
        get { return _cstrdisplayMember; }
        set { this._cstrdisplayMember = value; }

}

You have a similar problem with strValueMember.

Here is a reference to brush up on Properties[^]

Kornfeld Eliyahu Peter · Answer 2 · 2014-07-14T03:18:00

You have to learn what scope and access of a variable are!
You have here a read only property (and it's read only because it have only property getter, so you can only get its value):

C#

public string strDisplayMember
{
  get { return _cstrdisplayMember; }
}

To make it writable you have to add a property setter (which enables to set its value), something like this:

C#

public string strDisplayMember
{
  get { return _cstrdisplayMember; }
  set { _cstrdisplayMember = value; }
}

http://msdn.microsoft.com/en-us/library/w86s7x04.aspx[^]
---
Do yourself a favor and learn these basic elements of C# - do not write any code until you understand them by heart...

Duncan Edwards Jones · Answer 3 · 2014-07-14T03:14:00

Solution 1

You need a property setter

e.g.

C#

public string strDisplayMember
   {
       get { return _cstrdisplayMember; }
       set { cstrdisplayMember = value;}
   }

Otherwise the property is read-only

Posted 14-Jul-14 3:14am

Duncan Edwards Jones

Comments

chandra sekhar 14-Jul-14 9:33am

Now i am getting an error like LookupDTO lkpDTOo =(LookupDTO) obj; use of unassigned variable obj

johannesnestler 14-Jul-14 9:53am

back to basics for one day! You see, you don't know what to do with the solutions - exactly what I said in my first comment to you your question.

Duncan Edwards Jones 14-Jul-14 11:33am

object obj;

This object never gets assigned to anything. It is like you have got a fresh sheet of paper from the notepad and handed it to someone to read - but they can't because you have not written anything on it.

Sergey Alexandrovich Kryukov · Answer 4 · 2014-07-14T05:36:00

The whole idea to assign hard-coded immediate constant "--" in code is quite bad. You did not explain to us the goal of it. Anyway, here is how it looks: you specifically created a read-only member yourself and trying to assign a value to it. Your intention is hard to understand. Your already got technical advice in other solution, but I'm not sure they will solve your problem, which is just understanding of programming. You should understand every line you write.

—SA

Property or indexer cannot be assigned to "--" it is read only

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