Entity Framework not comparing byte arrays

Question

I am inserting data, using EF, which contains a SHA512 Hash. I am then looking up the same data like this, but no results are returned:

var searchHash = requestToFind.GetSelfSha512Hash();
var foundRequest = _complianceContext.ScoreResults
    .Where(sr => sr.SearchHash == searchHash);

Both sr.SearchHash and searchHash are byte[].

If I take out the Where clause, I do get 1 result. Any ideas why this may be?

Try this: Convert.ToBase64String(sr.SearchHash) == Convert.ToBase64String(searchHash) — Kevin
– Kevin, Commented Jan 25, 2017 at 21:19
What is the SQL type of SearchHash? Can you use SQL Profiler to determine what SQL Statement is being executed? — Theo
– Theo, Commented Jan 25, 2017 at 21:26

chadnt · Accepted Answer · 2017-01-25 21:25:20Z

10

The equality operator does not work like you expect for byte arrays. Try SequenceEqual.

var foundRequest = _complianceContext.ScoreResults
  .Where(sr => sr.SequenceEqual(searchHash));

answered Jan 25, 2017 at 21:25

chadnt

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1 Comment

chadnt Over a year ago

Based on the documentation, it is one pass through each byte array comparing corresponding bytes. I doubt that will have much impact. The only way to know for sure which approach is optimal is to profile.

Дмитрий Радчук · Accepted Answer · 2024-01-18 19:10:30Z

This is how I made EF 7 build queries that compare byte[] values:

Declared an empty method that accepts two byte arrays and returns bool in my context Class:

public partial class DbContext 
{
    public static bool LessThanOrEqual(byte[] a, byte[] b)
    {
       throw new NotImplementedException();
    }

In DbContetx.OnConfiguring() method defined a translation from this function to an SQL tree section:

modelBuilder.HasDbFunction(
    typeof(DbContext).GetMethod(nameof(LessThanOrEqual), new[] { typeof(byte[]), typeof(byte[]) }))
    .HasTranslation(
    args =>
        new SqlBinaryExpression(
            ExpressionType.LessThanOrEqual,
            args[0],
            args[1],
            args[0].Type,
            args[0].TypeMapping)
    );

Used this method in my Linq query:

    byte[] arr = ...
    db.tbl.Where(r => DbContext.LessThanOrEqual(r.arr1, arr) &&
                      DbContext.LessThanOrEqual(arr, r.arr2))

This Linq query produces the following SQL query:

    SELECT ...
    FROM tbl
    WHERE (b.arr1 <= @__arr_0) AND (@__arr_0 <= b.arr2)

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