Skip to main content

System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException: Operation is not valid due to the current state of the object.

You might have sometime faced the below exception while attempting to update an entity property:

System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException: Operation is not valid due to the current state of the object.

Reason:

After looking into the issue I found that this error occurs when an attempt is made to change a foreign key when the entity is already loaded. In this case, I was trying to assign a value to the foreign key property, and an exception is thrown as foreign key fields and association properties don’t match, when changes are submitted.

In such a scenario there are two values, one in the foreign key field or the one on the other side of the relationship and it doesn’t know which value is correct, and as a result exception is thrown.

Solution:

To avoid the exception the best way to update the relationship is by changing the association property and not the foreign keys. And then it will automatically keep the foreign keys in sync when you assign the association property a value.

The foreign key field value is changed only when there is either no association property defined on the object or the association property was never assigned a value.

For Example we have Address object and Country as it's child object, with foreign column is CountryId:

Then if we do
dbContext.Address.CountryId = newCountryId;

it'll raise exception, to avoid this update the relationship by changing the association property as:

dbContext.Address.Country = db.Country.Single(c => c.Id = newCountryId);
Labels:

Comments

Post a Comment

Popular posts from this blog

Error 405 : ASP.NET Core Web API PUT and DELETE Methods not allowed

Recently, while working with .Net core API I came across the issue of “Error 405 — Methods not Allowed” After some research, I found out that both GET and POST requests working fine but neither PUT nor DELETE requests working. Another thing is that the PUT and DELETE request was also working fine on my local machine but failed when we host on our Azure server. When I explored the issue on the web it led me to the conclusion that WebDAVModule seems to set PUT and DELETE request methods disabled by default and due to that PUT and DELETE throw 405 errors. To make the PUT and DELETE requests work, we need to override the WebDAVModule setting in web.config file by adding the below settings under “ system.webServer ”. < system.webServer >   < modules runAllManagedModulesForAllRequests = " false " >     < remove name = " WebDAVModule " />   </ modules > </ system.webServer > There may be 2 web.config files in y...
Post a Comment
Read more

C#: Merging Excel cells with NPOI HSSFWorkbook

In this post we’ll see how to merge the two or more cell with each other while creating the excel sheet using NPOI . Mentioned below is code to merge multiple cells, in this example we are merging first cell to fifth cell of first row (you can adjust row or cell range by passing particular parameters in CellRangeAddress). //Created new Workbook var hwb = new NPOI.HSSF.UserModel. HSSFWorkbook (); //Create worksheet with name. var sheet = hwb.CreateSheet( "new sheet" ); //Create row and cell. var row = sheet.CreateRow(0); var cell = row.CreateCell(0); ; //Set text inside cell cell.SetCellValue( "This is Merged cell" ); cell.CellStyle.WrapText = true ; //define cell range address // parameters: -> first row to last and first cell to last cell var cra = new NPOI.SS.Util. CellRangeAddress (0, 0, 0, 4); //Add merged region to sheet. sheet.AddMergedRegion(cra); Hope this solution helps you J
4 comments
Read more

How to set Swagger as the default start page for API hosted on the Azure web app?

I created an Asp.Net Core 2.x Web API and configured Swagger on it, below is the code added in Configure method under Startup.cs file, for full swagger configuration, check here //Add swagger configuration app.UseSwagger(); app.UseSwaggerUI(c => {     c.SwaggerEndpoint( "../swagger/v1/swagger.json" , "Test API V1" ); }); On my local machine when I run the API it is automatically redirected to the Swagger page. However, when I hosted this API as an Azure web app it is not redirecting directly to the Swagger and to access the swagger, I had to append /swagger in the URL, for example, https://testapi.azurewebsites.net/swagger/ Solution: Set RoutePrefix to string.Empty under app.UseSwaggerUI like below: app.UseSwaggerUI(c => {     c.SwaggerEndpoint( "../swagger/v1/swagger.json" , "Test API V1" );      c.RoutePrefix = string .Empty; // Set Swagger UI at apps root }); And that’s it, now when you b...
Post a Comment
Read more