Entity Framework Core 7 - Update produces error 'Cannot insert the value NULL into column'

I'm having a problem updating an object in EF Core 7. On an update (during the SaveChanges method), I get the following error:

Cannot insert the value NULL into column 'QueryName', table 'Lightwave360.dbo.Query'; column does not allow nulls. UPDATE fails

The object in question, Query, has a one-to-many relationship with another object, QueryParameter. The error message says the QueryName property is null. However, I'm 100% sure it is not null prior to the update.

Everything works correctly when I do a create/insert instead of an update. The update is the only thing that fails.

I'm hoping someone out there has had a similar issue. I've been trying to figure this out for a couple of days, but nothing has helped.

Here is the full error message:

SqlException: Cannot insert the value NULL into column 'QueryName', table 'Lightwave360.dbo.Query'; column does not allow nulls. UPDATE fails.

Here is my code - table definitions:

CREATE TABLE [Query]
(
    [QueryId] [int] IDENTITY(1,1) NOT NULL,
    [QueryName] [varchar](100) NOT NULL,
    [Sql] [ntext] NOT NULL,
    [ConnectionId] [int] NOT NULL,
    [Active] [bit] NOT NULL,
    [FolderId] [int] NOT NULL,
    [LastModifiedUser] [varchar](50) NULL,
    [LastModifiedDate] [datetime] NULL,

    CONSTRAINT [PK_Query] 
        PRIMARY KEY CLUSTERED ([QueryId] ASC)
                WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
                      IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, 
                      ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

CREATE TABLE [QueryParameter]
(
    [QueryParameterId] [int] IDENTITY(1,1) NOT NULL,
    [QueryId] [int] NOT NULL,
    [ParameterName] [varchar](25) NOT NULL,
    [ParameterType] [smallint] NOT NULL,
    [DataType] [smallint] NOT NULL,
    [Label] [varchar](50) NOT NULL,
    [DynamicParameterId] [int] NULL,
    [Required] [bit] NOT NULL,
    [DefaultValue] [varchar](254) NULL,
    [DisplayOrder] [smallint] NOT NULL,

    CONSTRAINT [PK_QueryParameter] 
        PRIMARY KEY CLUSTERED ([QueryParameterId] ASC)
                WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, 
                      IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, 
                      ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

CREATE UNIQUE NONCLUSTERED INDEX [IX_Query] 
ON [Query] ([QueryName] ASC)
       WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, 
             SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, 
             DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]

ALTER TABLE [QueryParameter] CHECK CONSTRAINT [FK_QueryParameter_Query]

Here are the class definitions:

[Table(nameof(Query))]
public partial class Query
{
    public Query() 
    { 
        QueryParameters = new List<QueryParameter>();
    }

    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int QueryId { get; set; }

    [Required]
    public string QueryName { get; set; }

    [Required]
    public string Sql { get; set; }

    [Required]
    public int ConnectionId { get; set; }

    public bool Active { get; set; } = true;

    [Required]
    public int FolderId { get; set; }

    public string? LastModifiedUser { get; set; }

    public DateTime? LastModifiedDate { get; set; }
    [ForeignKey(nameof(ConnectionId))]
    public virtual Connection Connection { get; set; }
    [ForeignKey(nameof(FolderId))]
    public virtual Folder Folder { get; set; }
    
    public ICollection<QueryParameter>? QueryParameters { get; set; }
}

[Table("QueryParameter", Schema = "dbo")]
public partial class QueryParameter
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int QueryParameterId { get; set; }

    [Required]
    public int QueryId { get; set; }

    [Required]
    public string ParameterName { get; set; }

    [Required]
    public QueryParameterType ParameterType { get; set; }

    [Required]
    public QueryParameterDataType DataType { get; set; }

    [Required]
    public string Label { get; set; }

    public int? DynamicParameterId { get; set; }

    public bool Required { get; set; }

    public string DefaultValue { get; set; }

    public short DisplayOrder { get; set; }

    [ForeignKey(nameof(DynamicParameterId))]
    public DynamicParameter DynamicParameter { get; set; }

    [ForeignKey(nameof(QueryId))]
    public Query Query { get; set; }
}

Here is the update code:

public IActionResult PutQuery(int key, [FromBody] Lightwave.Data.Query item)
{
        try
        {
            ModelState.Clear();
            //if(!ModelState.IsValid)
            //{
            //    return BadRequest(ModelState);
            //}

            if(item == null || (item.QueryId != key))
            {
                return BadRequest();
            }

            item.LastModifiedDate = DateTime.Now;
            OnQueryUpdated(item);

            _context.Queries.Update(item);
            _context.SaveChanges();

            var itemToReturn = _context.Queries
                .Include(i => i.Connection)
                .Include(i => i.Folder)
                .Include(i => i.QueryParameters)
                .Where(i => i.QueryId == key);
            Request.QueryString = Request.QueryString.Add("$expand", "Connection");
            OnAfterQueryUpdated(item);

            return new ObjectResult(SingleResult.Create(itemToReturn));
        }
        catch(Exception ex)
        {
            ModelState.AddModelError("", ex.GetBaseException().Message);
            _logger.LogError(ex.GetBaseException(), ex.GetBaseException().Message);
            return BadRequest(ModelState);
        }
}

If anyone has any suggestions, I would greatly appreciate it. As I've said, I've been working on this for a couple of days and have exhausted all efforts that I can think of.

Thanks.

UPDATE: I'm still trying to figure this thing out. I wanted to add the SQL that is being generated on the backend during the Update/SaveChanges(). It looks as though it is deleting the entity, then inserting it back. Again, if anyone can help out, it would be greatly appreciated. Here is the generated SQL:

exec sp_executesql N'SET NOCOUNT ON;
DELETE FROM [Query]
OUTPUT 1
WHERE [QueryId] = @p0;
MERGE [Query] USING (
VALUES (@p1, @p2, @p3, @p4, @p5, @p6, @p7, 0),
(@p8, @p9, @p10, @p11, @p12, @p13, @p14, 1)) AS i ([Active], [ConnectionId], [FolderId], [LastModifiedDate], [LastModifiedUser], [QueryName], [Sql], _Position) ON 1=0
WHEN NOT MATCHED THEN
INSERT ([Active], [ConnectionId], [FolderId], [LastModifiedDate], [LastModifiedUser], [QueryName], [Sql])
VALUES (i.[Active], i.[ConnectionId], i.[FolderId], i.[LastModifiedDate], i.[LastModifiedUser], i.[QueryName], i.[Sql])
OUTPUT INSERTED.[QueryId], i._Position;
',N'@p0 int,@p1 bit,@p2 int,@p3 int,@p4 datetime2(7),@p5 nvarchar(4000),@p6 nvarchar(4000),@p7 nvarchar(4000),@p8 bit,@p9 int,@p10 int,@p11 datetime2(7),@p12 nvarchar(4000),@p13 nvarchar(4000),@p14 nvarchar(4000)',@p0=10,@p1=1,@p2=1,@p3=0,@p4=NULL,@p5=NULL,@p6=NULL,@p7=NULL,@p8=1,@p9=0,@p10=1,@p11=NULL,@p12=NULL,@p13=NULL,@p14=NULL