HTTP PATCH - one DTO to patch multiple Entities

Question

My current implementation has two http.PatchAsync() calls to the Web API, i.e. to multiple controller action methods, one for each Entity.

Thought that I could improve on this by sending one DTO containing the data the needs to be updated for multiple Entities, only one packet at risk of loss vs. multiple.

Now I have hit a road block as I cannot find how to use the same JsonPatchDocument for several Entities

Code so far:

[Route("UpdatePartial/{id}")]  /
        [HttpPatch]
        public async Task<IActionResult> Patch(int id, bool hasQbWc, [FromBody] JsonPatchDocument<TxnBillingPatch> txnPatch)
        {
            if (txnPatch == null) { return BadRequest(); }

            var theTxn = context.Transactions.FirstOrDefault(t => t.TransactionId == id);

            if (theTxn == null) { return NotFound(); }
            **txnPatch.ApplyTo(theTxn, ModelState);**

            var isValid = TryValidateModel(theTxn);
            if (!isValid) { return BadRequest(ModelState);  }

            //await context.SaveChangesAsync();
            return NoContent();
        }

Squiggles on the bolded line with "cannot convert from Transaction (the Entity) to TxnBillingPatch (the DTO)

Answer 1

Hi @wavemaster ,

You need change like below:

    [Route("UpdatePartial/{id}")]  
    [HttpPatch]  
    public async Task<IActionResult> Patch(int id, bool hasQbWc, [FromBody] JsonPatchDocument<TxnBillingPatch> txnPatch)  
    {  
        if (txnPatch == null) { return BadRequest(); }  
        var theTxn = new Transaction() { Id = 1, TransName = "trans1" };  
          
       //add this....  
        var data = new TxnBillingPatch();        
        data.Transaction = theTxn;  
        txnPatch.ApplyTo(data, ModelState);   
  
        var isValid = TryValidateModel(theTxn);  
        if (!isValid) { return BadRequest(ModelState); }  
  
        //await context.SaveChangesAsync();  
        return new ObjectResult(data);  
    }  

JSON patch example:

[  
    {  
        "op":"add",  
        "path":"/TestViewModel",  
        "value":[{  
            "id":1,  
            "testName":"aa"  
        }]  
    }  
]  

Result:

{  
    "transaction": {  
        "id": 1,  
        "transName": "trans1"  
    },  
    "testViewModel": [  
        {  
            "id": 1,  
            "testName": "aa"  
        }  
    ]  
}  

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Best Regards,

Rena