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Try Cath with return - how to do that
f#

I have this C# code

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public bool TryGetSetting<T>(string key, out T value){
    try{
        var str = ConfigurationManager.AppSettings.Get(key);
        if(str == null){
            value = default(T);
            return false;
        }
        value = (T)Convert.ChangeType(str, typeof(T));
        return true;
    }catch(FormatException){
        value = default(T);
        return false;
    }
}

I tried this

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member x.TryGetSetting (key:string, value:'c byref) =
            let result = 
                try
                    let str = ConfigurationManager.AppSettings.Get(key)
                    if str <> null then
                        value <- Convert.ChangeType(str, typeof<'c>) :?> 'c
                        true
                    else
                        value <- Unchecked.defaultof<'c>
                        false
                with
                | :? ArgumentException -> false
                | _ -> rethrow()
            result

but it won't compile

.

OK I got it it was

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member x.TryGetSetting (key:string, value:'c byref):bool =
            try
                let str = ConfigurationManager.AppSettings.Get(key)
                if str <> null then
                    value <- (Convert.ChangeType(str, typeof<'c>) :?> 'c)
                    true
                else
                    value <- Unchecked.defaultof<'c>
                    false
            with
            | :? ArgumentException -> false
            | _ -> rethrow()

The key was to change that

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value <- Convert.ChangeType(str, typeof<'c>) :?> 'c

into that 

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value <- (Convert.ChangeType(str, typeof<'c>) :?> 'c)
By on 4/17/2009 11:15 AM ()

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