I have a relationship on project entity and employee entity. In there I need have added a one to many relationship using entity framework core.(One employee have many projects but one project has one employee) The get,post,delete requests are working fine but the update request us failing.

this is my project enttiy

using HRM_API.Entity;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace HRM_API.Entities
{
    public class Project
    {
        [Key]
        public Guid ProjectID { get; set; }

        [MaxLength(1000)]
        public string? ProjectTitle { get; set; }

        [MaxLength(1000)]
        public string? Description { get; set; }

        [Column("fk_emp_id")]
        public Guid? employeeID { get; set; }

        //Navigation Properties
        public Employee? employee { get; set; }

    }
}

This is my employee entity

using HRM_API.Entities;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace HRM_API.Entity
{
    public class Employee
    {
        [Key]
        public Guid EmpId { get; set; }

        [MaxLength(200)]
        public string? FirstName { get; set; }

        [MaxLength(200)]
        public string? MiddleName { get; set; }

        [MaxLength(600)]
        public string? FullName { get; set; }

        //Navigation Properties
         public ICollection<Project> projects { get; set; } = new List<Project>();

    }
}

this is the relationship dbContext

 //employee and project ralationship one to many
  modelBuilder.Entity<Employee>()
       .HasMany(e => e.projects)
       .WithOne(q => q.employee)
       .HasForeignKey(q => q.employeeID)
       .OnDelete(DeleteBehavior.SetNull);

When I am updating a project details it throws this exception.

Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while saving the entity changes. See the inner exception for details.
 ---> Microsoft.Data.SqlClient.SqlException (0x80131904): The UPDATE statement conflicted with the FOREIGN KEY constraint "FK_projects_employees_fk_emp_id". The conflict occurred in database "HRM-DB", table "dbo.employees", column 'EmpId'.
   at Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.SqlDataReader.TryHasMoreRows(Boolean& moreRows)
   at Microsoft.Data.SqlClient.SqlDataReader.TryReadInternal(Boolean setTimeout, Boolean& more)
   at Microsoft.Data.SqlClient.SqlDataReader.ReadAsyncExecute(Task task, Object state)
   at Microsoft.Data.SqlClient.SqlDataReader.InvokeAsyncCall[T](SqlDataReaderBaseAsyncCallContext`1 context)
--- End of stack trace from previous location ---
   at Microsoft.EntityFrameworkCore.Update.AffectedCountModificationCommandBatch.ConsumeResultSetWithRowsAffectedOnlyAsync(Int32 commandIndex, RelationalDataReader reader, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.AffectedCountModificationCommandBatch.ConsumeAsync(RelationalDataReader reader, CancellationToken cancellationToken)
ClientConnectionId:0a4d8f25-5efd-4c0b-b095-3c3c94de94d7
Error Number:547,State:0,Class:16
   --- End of inner exception stack trace ---
   at Microsoft.EntityFrameworkCore.Update.AffectedCountModificationCommandBatch.ConsumeAsync(RelationalDataReader reader, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.SqlServer.Update.Internal.SqlServerModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList`1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at HRM_API.Repositories.ProjectRepository.UpdateProjectByID(Guid projectID, Project updatedProject) in H:Company projectsHRM-SystemBackEndRepositoriesProjectRepository.cs:line 62
   at HRM_API.Services.ProjectService.UpdateProject(Guid projectID, UpdateProjectDto updateProjectDto) in H:Company projectsHRM-SystemBackEndServicesProjectService.cs:line 65
   at HRM_API.Controllers.ProjectController.UpdateProject(Guid projectID, UpdateProjectDto dto) in H:Company projectsHRM-SystemBackEndControllersProjectController.cs:line 51
   at lambda_method989(Closure, Object)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfActionResultExecutor.Execute(ActionContext actionContext, IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|7_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.<Invoke>g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)
[16:23:28 DBG] 'HrmDbContext' disposed.

Addtionally this is the updated request dto .

using System.ComponentModel.DataAnnotations;

namespace HRM_API.Models.Project
{
    public class UpdateProjectDto
    {
        [Required]
        [MinLength(4)]
        [MaxLength(1000)]
        public string? ProjectTitle { get; set; }

        [Required]
        public Guid EmpId { get; set; }

        [Required]
        [MinLength(4)]
        [MaxLength(1000)]
        public string? Description { get; set; }
    }
}

This is the repository method for update project.

 public async Task<Project> UpdateProjectByID(Guid projectID, Project updatedProject )
 {
     Project existing = await FindProjectByID(projectID);

     existing.ProjectTitle = updatedProject.ProjectTitle;
     existing.Description = updatedProject.Description;
     existing.employeeID = updatedProject.employeeID;

     await dbContext.SaveChangesAsync();
     return existing;

 }

Guide me how to overcome this error