LINQ to Entities不支持实体框架'ArrayIndex'

Question

in my SQL Server DB table, I have the binary column type.

I can't execute the query, why ?

var data = (from x in model.MyTable
            where x.BinaryColumn[0] == 1
            select x).FirstOrDefault();

I get the The LINQ expression node type 'ArrayIndex' is not supported in LINQ to Entities error

Answer 1

These expressions are translated to SQL queries, and this is one of the things you cant do. Take a look here for more detail: LINQ To Entities doesn't recognize array index

Answer 2

In TSQL the SUBSTRING function can be used on binary / varbinary .

Somewhere define:

[DbFunction("SqlServer", "SUBSTRING")]
public static byte[] SubString(byte[] field, int start, int length)
{
    throw new NotSupportedException("Direct calls are not supported.");
}

then

var data = (from x in model.MyTable
            where Substring(x.BinaryColumn, 1, 1) == new byte[] { 1 }
            select x).FirstOrDefault();

Answer 3

If you're willing to change your query a bit, this would work:

var data = (from x in model.MyTable
            where SqlFunctions.CharIndex(new byte[] { 1 }, x.BinaryColumn) == 1
            select x).FirstOrDefault();

See MSDN