JOIN conditions in EF-CodePudding

I am working on an application that uses EF to access the database. We have a fairly convoluted model and use relationships to let EF automatically join tables into the model objects.

We have a table called product_data that links to many product_attribute entries. When joining the two, I'd like EF to check the product_attribute.Delete_Time to make sure the entry wasn't deleted.

How do I configure such a condition?

CodePudding user response：

If you have configured properly the connections between the tables


var result = await this.context.ProductData
      .Include(x => x.ProductAttribute)
      .Where(x => x.ProductAttribute.DeleteTime == "deleteTime")
      .ToListAsync();

CodePudding user response：

To configure a condition in Entity Framework (EF) to check the Delete_Time column of the product_attribute table when joining it to the product_data table, you can use a LINQ query with a Where clause to filter the results.

Here is an example of how you might do this:

using (var context = new MyDbContext())
{
    var query = from pd in context.ProductData
                join pa in context.ProductAttribute on pd.ProductId equals pa.ProductId
                where pa.DeleteTime == null
                select pd;

    var results = query.ToList();
}

This LINQ query will join the ProductData and ProductAttribute tables, and the Where clause will filter out any ProductAttribute entries that have a non-null value in the DeleteTime column.

Alternatively, you can use the Include method to specify the related ProductAttribute entries to include in the query, and use the ThenInclude method to filter the results using a lambda expression:

using (var context = new MyDbContext())
{
    var query = context.ProductData
        .Include(pd => pd.ProductAttribute)
        .ThenInclude(pa => pa.Where(x => x.DeleteTime == null));

    var results = query.ToList();
}

This will include the related ProductAttribute entries in the query, and the lambda expression will filter out any entries with a non-null DeleteTime value.