Question

Let’s say I have the following tables:

class Module
{
    long MID    // PK
    string Name
}

class ModuleBlock
{
    long MID      // FK
    long BID      // FK
}

class Block
{
    long BID      // PK
    string Info
}

I want to select all the Blocks that do NOT have a BID in ModuleBlocks.

How do I do this query?

I’m pretty sure it’s something along the lines of join Blocks with ModuleBlocks on BID and check the nulls but how do I do this in LINQ?

Answer 1

Not sure about the ‘nulls’ since you do not give any nullable properties in your pseudo-code. But the LINQ query would/could be something like this I think:

List<Module> modules = ...
List<ModuleBlock> moduleBlocks = ...
List<Block> blocks = ...

var blocksWithNoBidsInModuleBlocks = blocks
   .Where(b => !moduleBlocks.Select(mb => mb.BID).Contains(b.BID)).ToList();