Generic converter

Requested converter does not exist. If boolean value is TRUE, then return 1, else return 0. Labels: Utility. Newer Post Older Post Home. Subscribe to: Post Comments Atom.

About BalusC View my complete profile. The TOutput that represents the converted TInput. This section contains two code examples. The ConvertAll method passes each element of the input list to the PointFToPoint method and puts the converted elements into a new list of Point structures.

Both lists are displayed. Skip to main content. This browser is no longer supported. In the code you write for a custom converter, be aware of the substantial performance penalty for using new JsonSerializerOptions instances.

For more information, see Reuse JsonSerializerOptions instances. Visual Basic can't be used to write custom converters but can call converters that are implemented in C libraries.

For more information, see Visual Basic support. There are two patterns for creating a custom converter: the basic pattern and the factory pattern. The factory pattern is for converters that handle type Enum or open generics.

The basic pattern is for non-generic and closed generic types. For example, converters for the following types require the factory pattern:. The basic pattern creates a class that can handle one type. The factory pattern creates a class that determines, at run time, which specific type is required and dynamically creates the appropriate converter. The following sample is a converter that overrides default serialization for an existing data type.

The code follows the factory pattern because the first generic type parameter is Enum and the second is open. The CanConvert method returns true only for a Dictionary with two generic parameters, the first of which is an Enum type.

The inner converter gets an existing converter to handle whichever type is provided at run time for TValue. The preceding code is the same as what is shown in the Support Dictionary with non-string key later in this article.

You can refer to the built-in converters source code as reference implementations for writing custom converters. The factory pattern is required for open generics because the code to convert an object to and from a string isn't the same for all types.

Code must be written to handle each closed-generic type that the converter can handle. The Enum type is similar to an open generic type: a converter for Enum has to create a converter for a specific Enum WeekdaysEnum , for example behind the scenes. You must then read through all the tokens in that object and exit the method with the reader positioned on the corresponding end object token. If you read beyond the end of the object, or if you stop before reaching the corresponding end token, you get a JsonException exception indicating that:.

For an example, see the preceding factory pattern sample converter. The Read method starts by verifying that the reader is positioned on a start object token. It reads until it finds that it is positioned on the next end object token. It stops on the next end object token because there are no intervening start object tokens that would indicate an object within the object. The same rule about begin token and end token applies if you are converting an array.

The serializer provides special handling for exception types JsonException and NotSupportedException. If you throw a JsonException without a message, the serializer creates a message that includes the path to the part of the JSON that caused the error. For example, the statement throw new JsonException produces an error message like the following example:. If you throw a NotSupportedException , you always get the path information in the message.

If you provide a message, the path information is appended to it. For example, the statement throw new NotSupportedException "Error occurred. When you want to disallow certain types, throw a NotSupportedException. This exception is what the serializer automatically throws for types that are not supported. For example, System. Type is not supported for security reasons, so an attempt to deserialize it results in a NotSupportedException. You can throw other exceptions as needed, but they don't automatically include JSON path information.

Register a custom converter to make the Serialize and Deserialize methods use it. Choose one of the following approaches:. GetConverter typeof T ; if converter. Bradley Uffner 16k 3 3 gold badges 39 39 silver badges 63 63 bronze badges.

Yes, that makes even more generic. Good suggestion. I strongly recommend avoiding many catch blocks that do the exact same thing, consider using when instead. Also regarding "only catch the exceptions you know of", IMO that's a judgement call, if you use catch Exception you are assuming that if the framework class throws an exception, it will be recoverable; if you catch only known exceptions, you are assuming that the entire framework has demolished itself irrecoverably but has not used a CSE exception type.

I would argue that the former is more likely and I have ran into it in the past. Admittedly the handling of this "roll back" is nontrivial and must be done carefully. But you should add a small additional check here, too: if! CanConvertFrom typeof string return false; Additionally, I would mention that you should use the ConvertFromInvariantString method if you do not want trouble with the different region settings in case of floating point values, for example About the ConvertFromInvariantString that is a good tip I was having problems with converting doubles with ".

But using the second option I could pass an IFormatProvider That solves that problem on the second example, right? Yes, using a specified culture solves the problem, too. Btw, you can convert from any object source here, too. Just use the CanConvertFrom Type method. Community Bot 1 1 1 silver badge.