How to declare a static dictionary object inside a static class? I tried
public static class ErrorCode
{
public const IDictionary<string, string> ErrorCodeDic = new Dictionary<string, string>()
{
{ "1", "User name or password problem" }
};
}
But the compiler complains that "A const field of a reference type other than string can only be initialized with null".
This question is related to
c#
.net
dictionary
public static class ErrorCode
{
public const IDictionary<string , string > m_ErrorCodeDic;
public static ErrorCode()
{
m_ErrorCodeDic = new Dictionary<string, string>()
{ {"1","User name or password problem"} };
}
}
Probably initialise in the constructor.
Create a static constructor to add values in the Dictionary
enum Commands
{
StudentDetail
}
public static class Quires
{
public static Dictionary<Commands, String> quire
= new Dictionary<Commands, String>();
static Quires()
{
quire.add(Commands.StudentDetail,@"SELECT * FROM student_b");
}
}
public static class ErrorCode
{
public const IDictionary<string , string > m_ErrorCodeDic;
public static ErrorCode()
{
m_ErrorCodeDic = new Dictionary<string, string>()
{ {"1","User name or password problem"} };
}
}
Probably initialise in the constructor.
Make the Dictionary a static, and never add to it outside of your static object's ctor. That seems to be a simpler solution than fiddling with the static/const rules in C#.
OK - so I'm working in ASP 2.x (not my choice...but hey who's bitching?).
None of the initialize Dictionary examples would work. Then I came across this: http://kozmic.pl/archive/2008/03/13/framework-tips-viii-initializing-dictionaries-and-collections.aspx
...which hipped me to the fact that one can't use collections initialization in ASP 2.x.
Create a static constructor to add values in the Dictionary
enum Commands
{
StudentDetail
}
public static class Quires
{
public static Dictionary<Commands, String> quire
= new Dictionary<Commands, String>();
static Quires()
{
quire.add(Commands.StudentDetail,@"SELECT * FROM student_b");
}
}
Make the Dictionary a static, and never add to it outside of your static object's ctor. That seems to be a simpler solution than fiddling with the static/const rules in C#.
The correct syntax ( as tested in VS 2008 SP1), is this:
public static class ErrorCode
{
public static IDictionary<string, string> ErrorCodeDic;
static ErrorCode()
{
ErrorCodeDic = new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
}
public static class ErrorCode
{
public const IDictionary<string , string > m_ErrorCodeDic;
public static ErrorCode()
{
m_ErrorCodeDic = new Dictionary<string, string>()
{ {"1","User name or password problem"} };
}
}
Probably initialise in the constructor.
The correct syntax ( as tested in VS 2008 SP1), is this:
public static class ErrorCode
{
public static IDictionary<string, string> ErrorCodeDic;
static ErrorCode()
{
ErrorCodeDic = new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
}
The problem with your initial example was primarily due to the use of const rather than static; you can't create a non-null const reference in C#.
I believe this would also have worked:
public static class ErrorCode
{
public static IDictionary<string, string> ErrorCodeDic
= new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
Also, as Y Low points out, adding readonly is a good idea as well, and none of the modifiers discussed here will prevent the dictionary itself from being modified.
Make the Dictionary a static, and never add to it outside of your static object's ctor. That seems to be a simpler solution than fiddling with the static/const rules in C#.
The problem with your initial example was primarily due to the use of const rather than static; you can't create a non-null const reference in C#.
I believe this would also have worked:
public static class ErrorCode
{
public static IDictionary<string, string> ErrorCodeDic
= new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
Also, as Y Low points out, adding readonly is a good idea as well, and none of the modifiers discussed here will prevent the dictionary itself from being modified.
You can use the static/class constructor to initialize your dictionary:
public static class ErrorCode
{
public const IDictionary<string, string> ErrorCodeDic;
public static ErrorCode()
{
ErrorCodeDic = new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
}
OK - so I'm working in ASP 2.x (not my choice...but hey who's bitching?).
None of the initialize Dictionary examples would work. Then I came across this: http://kozmic.pl/archive/2008/03/13/framework-tips-viii-initializing-dictionaries-and-collections.aspx
...which hipped me to the fact that one can't use collections initialization in ASP 2.x.
public static class ErrorCode
{
public const IDictionary<string , string > m_ErrorCodeDic;
public static ErrorCode()
{
m_ErrorCodeDic = new Dictionary<string, string>()
{ {"1","User name or password problem"} };
}
}
Probably initialise in the constructor.
The problem with your initial example was primarily due to the use of const rather than static; you can't create a non-null const reference in C#.
I believe this would also have worked:
public static class ErrorCode
{
public static IDictionary<string, string> ErrorCodeDic
= new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
Also, as Y Low points out, adding readonly is a good idea as well, and none of the modifiers discussed here will prevent the dictionary itself from being modified.
Make the Dictionary a static, and never add to it outside of your static object's ctor. That seems to be a simpler solution than fiddling with the static/const rules in C#.
You can use the static/class constructor to initialize your dictionary:
public static class ErrorCode
{
public const IDictionary<string, string> ErrorCodeDic;
public static ErrorCode()
{
ErrorCodeDic = new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
}
Old question, but I found this useful. Turns out, there's also a specialized class for a Dictionary using a string for both the key and the value:
private static readonly StringDictionary SegmentSyntaxErrorCodes = new StringDictionary
{
{ "1", "Unrecognized segment ID" },
{ "2", "Unexpected segment" }
};
Edit: Per Chris's comment below, using Dictionary<string, string> over StringDictionary is generally preferred but will depend on your situation. If you're dealing with an older code base, you might be limited to the StringDictionary. Also, note that the following line:
myDict["foo"]
will return null if myDict is a StringDictionary, but an exception will be thrown in case of Dictionary<string, string>. See the SO post he mentioned for more information, which is the source of this edit.
The problem with your initial example was primarily due to the use of const rather than static; you can't create a non-null const reference in C#.
I believe this would also have worked:
public static class ErrorCode
{
public static IDictionary<string, string> ErrorCodeDic
= new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
Also, as Y Low points out, adding readonly is a good idea as well, and none of the modifiers discussed here will prevent the dictionary itself from being modified.
You can use the static/class constructor to initialize your dictionary:
public static class ErrorCode
{
public const IDictionary<string, string> ErrorCodeDic;
public static ErrorCode()
{
ErrorCodeDic = new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
}
The correct syntax ( as tested in VS 2008 SP1), is this:
public static class ErrorCode
{
public static IDictionary<string, string> ErrorCodeDic;
static ErrorCode()
{
ErrorCodeDic = new Dictionary<string, string>()
{ {"1", "User name or password problem"} };
}
}
Source: Stackoverflow.com