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Thread: an item with the same key has already been added.

  1. #1

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    an item with the same key has already been added.

    in mvc how can i solve an item with the same key has already been added issue.
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  2. #2
    .NUT jmcilhinney's Avatar
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    Re: an item with the same key has already been added.

    You're going to have to provide much more information than that. You need to describe exactly what circumstances under which you got that error message. You need to provide a FULL and CLEAR explanation of the problem.

  3. #3
    PowerPoster kfcSmitty's Avatar
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    Re: an item with the same key has already been added.

    To add what jmc said, you need to not add the same key.

  4. #4
    Super Moderator dday9's Avatar
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    Re: an item with the same key has already been added.

    I can only speculate as to what is causing this issue, but I suspect that you have declared a Dictionary(Of TKey, TValue) and you're attempting to add multiple records, but one of these records share the same key.

    If you're taking in a JSON request then attempt to deserialize to a List(Of T) where the type is a KeyValuePair. This is so you can setup a break point, get all the Keys from the KeyValuePairs, and find the duplicate in the intermediate winow.

  5. #5
    .NUT jmcilhinney's Avatar
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    Re: an item with the same key has already been added.

    Quote Originally Posted by kfcSmitty View Post
    To add what jmc said, you need to not add the same key.
    Quote Originally Posted by dday9 View Post
    I can only speculate as to what is causing this issue, but I suspect that you have declared a Dictionary(Of TKey, TValue) and you're attempting to add multiple records, but one of these records share the same key.

    If you're taking in a JSON request then attempt to deserialize to a List(Of T) where the type is a KeyValuePair. This is so you can setup a break point, get all the Keys from the KeyValuePairs, and find the duplicate in the intermediate winow.
    I don't think that this is a case of explicitly adding an item to your own Dictionary. I've seen this type of error before in MVC but I can't recall the specific cause or whether it's always the same. The Dictionary in question is something within MVC and I think that it might have something to do with model binding; perhaps two fields in a view trying to generate field son the model with the same name or something like that. Of course, the same rules apply as when debugging anything, i.e. just stating the error message with no context is rarely enough.

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