Entity Framework. Delete all rows in table

Solution 1:

For those that are googling this and ended up here like me, this is how you currently do it in EF5 and EF6:

context.Database.ExecuteSqlCommand("TRUNCATE TABLE [TableName]");

Assuming context is a System.Data.Entity.DbContext

Solution 2:

Warning: The following is only suitable for small tables (think < 1000 rows)

Here is a solution that uses entity framework (not SQL) to delete the rows, so it is not SQL Engine(R/DBM) specific.

This assumes that you're doing this for testing or some similar situation. Either

• The amount of data is small or
• The performance doesn't matter

Simply call:

VotingContext.Votes.RemoveRange(VotingContext.Votes);

Assuming this context:

public class VotingContext : DbContext
{
    public DbSet<Vote> Votes{get;set;}
    public DbSet<Poll> Polls{get;set;}
    public DbSet<Voter> Voters{get;set;}
    public DbSet<Candidacy> Candidates{get;set;}
}

For tidier code you can declare the following extension method:

public static class EntityExtensions
{
    public static void Clear<T>(this DbSet<T> dbSet) where T : class
    {
        dbSet.RemoveRange(dbSet);
    }
}

Then the above becomes:

VotingContext.Votes.Clear();
VotingContext.Voters.Clear();
VotingContext.Candidacy.Clear();
VotingContext.Polls.Clear();
await VotingTestContext.SaveChangesAsync();

I recently used this approach to clean up my test database for each testcase run (it´s obviously faster than recreating the DB from scratch each time, though I didn´t check the form of the delete commands that were generated).

Why can it be slow?

1. EF will get ALL the rows (VotingContext.Votes)
2. and then will use their IDs (not sure exactly how, doesn't matter), to delete them.

So if you're working with serious amount of data you'll kill the SQL server process (it will consume all the memory) and same thing for the IIS process since EF will cache all the data same way as SQL server. Don't use this one if your table contains serious amount of data.