SqlBulkCopy Insert with Identity Column

To have the destination table assign the identity, DO NOT use the SqlBulkCopyOptions.KeepIdentity option. Instead, don't map the identity from the source, and don't extract it from source to send through to SqlBulkCopy.

You have two options -

1 - use KeepIdentity and preserve the source's Identity values.

2 - Don't map the Identity field. If you don't try to assign a value the target table will assign one automatically.

Fill the ColumnMapping of the BulkCopy object and don't map the identity column. The identity column will be generated by the target database.

This is the table

CREATE TABLE [dbo].[ProductShippingMethodMap](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [ProductId] [int] NOT NULL,
    [ShippingMethodId] [int] NOT NULL,
    [ParentProductId] [int] NOT NULL,
 CONSTRAINT [PK_ProductShippingMethodMap] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO

The bellow C# code is working

 DataTable dtQtyData = new DataTable();
        dtQtyData.Clear();
        dtQtyData.Columns.Add("Id", typeof(int));

    dtQtyData.Columns.Add("ProductId", typeof(int));
    dtQtyData.Columns.Add("ShippingMethodId", typeof(int));
    dtQtyData.Columns.Add("ParentProductId", typeof(int));


    for (int i = 0; i < ShippingMethodIds.Length; i++)
    {
        for (int j = 0; j < ProductIds.Length; j++)
        {
            var productId = ProductIds[j];
            var shippingMethodId = ShippingMethodIds[i];
            dtQtyData.Rows.Add(new object[] {0,productId, shippingMethodId, parentProductId });
        }

    }
    var connectionString = new DataSettingsManager().LoadSettings().DataConnectionString;
    SqlBulkCopy bulkcopy = new SqlBulkCopy(connectionString, SqlBulkCopyOptions.Default);
    bulkcopy.DestinationTableName = "ProductShippingMethodMap";
    bulkcopy.WriteToServer(dtQtyData);