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The RelistFixedPriceItem call can be used to to relist fixed-price item that has ended. It is recommended to use this call instead of creating a new listing using the AddFixedPriceItem call to take advantage of the recent sales score associated with the listing.
Here is a C# RelistFixedPriceItem sample for re-listing an item with some minor modifications (title updated. subtitle deleted) This sample has been written using the .NET SDK.
Below is the code. Corresponding SOAP request is attached with this article.
Console.WriteLine(relistFP.ApiResponse.Ack + " Relisted SKU. The new ItemID is " + relistFP.ItemID);