.Net Core EF doesn't allow me to enter same Foreign Key - asp.net-core

Question

I have got a Model with Foreign Key. Some how .NET Core EF doesn't let me enter the same Foreign key twice to the table.
public class DolsMcaClientModel
{
[Key]
public int DolsMcaClientID { get; set; }
public int DolsMcaItemID { get; set; }
public virtual DolsMcaItemModel DolsMcaItemModel { get; set; }
public int ClientID { get; set; }
[Required]
public int FileID { get; set; }
public virtual FileModel FileModel { get; set; }
}
In this table DolsMcaClientID is my Identity Column and DolsMcaItemID is my Foreign column. DolsMcaItemModel is my navigation property.
I can't enter the same DolsMcaItemID for different client.
DolsMcaItemID acting like a primary key in the table. But it is not.
ERROR: System.Data.SqlClient.SqlException: Cannot insert duplicate key row in object 'dbo.DolsMcaClientModels' with unique index 'IX_DolsMcaClientModels_DolsMcaItemID'. The duplicate key value is (1).
If I delete DolsMcaItemID 1 item from the table, then i can add new entry to the table with DolsMcaItemId 1, but only once with any clientID... i can't enter DolsMcaItem 1 for with any other clientID
My SQL Table create query is:
CREATE TABLE [dbo].[DolsMcaClientModels](
[DolsMcaClientID] [int] IDENTITY(1,1) NOT NULL,
[DolsMcaItemID] [int] NOT NULL,
[ClientID] [int] NOT NULL,
[FileID] [int] NOT NULL,
CONSTRAINT [PK_DolsMcaClientModels] PRIMARY KEY CLUSTERED
(
[DolsMcaClientID] 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]
GO
ALTER TABLE [dbo].[DolsMcaClientModels] WITH CHECK ADD CONSTRAINT [FK_DolsMcaClientModels_DolsMcaItemModels_DolsMcaItemID] FOREIGN KEY([DolsMcaItemID])
REFERENCES [dbo].[DolsMcaItemModels] ([DolsMcaItemID])
ON DELETE CASCADE
GO
ALTER TABLE [dbo].[DolsMcaClientModels] CHECK CONSTRAINT [FK_DolsMcaClientModels_DolsMcaItemModels_DolsMcaItemID]
GO
ALTER TABLE [dbo].[DolsMcaClientModels] WITH CHECK ADD CONSTRAINT [FK_DolsMcaClientModels_FileModels_FileID] FOREIGN KEY([FileID])
REFERENCES [dbo].[FileModels] ([FileID])
ON DELETE CASCADE
GO
ALTER TABLE [dbo].[DolsMcaClientModels] CHECK CONSTRAINT [FK_DolsMcaClientModels_FileModels_FileID]
GO

Answer 1

The UNIQUE index [IX_DolsMcaClientModels_DolsMcaItemID] on that column is preventing you from committing another record with the same [DolsMcaItemID].
Fix is to drop the unique index:
ALTER TABLE [dbo].[DolsMcaClientModels] DROP INDEX [IX_DolsMcaClientModels_DolsMcaItemID];
CREATE INDEX [IX_DolsMcaClientModels_DolsMcaItemID] ON [dbo].[DolsMcaClientModels] ([DolsMcaItemID])
Don't forget to scaffold your db context to remove the constraint from code.