当作为谓词传递时，实体框架 Linq 查询不会在 SQL 服务器中生成 where 子句

Question

I've created a brand new Project in .NET Core 3.1 and a query I am creating is generating a SQL query (viewed in SQL Server Profiler) that does not contain a where clause and instead reads in the entire table. Is there a way to pass in a predicate and have that incorporated into the SQL statement that is ultimately generated?

In the below function query1 is an IQueryable<Balance> and query2 is an IEnumerable<Balance> :

    public int GetCount(Func<Balance, bool> predicate)
    {
        var query1 = (from b in _appContext.Balance
                      select b
                      );
        var query2 = query1.Where(predicate);
        var count = query2.Count();

        return count;
    }

Called like this:

    GetCount(p => p.Email == 'test@gmail.com');

Answer 1

This answer helped me out: Create Expression from Func .

Basically I had to wrap the Func in an Expression as follows:

    public int GetCount(Expression<Func<Balance, bool>> predicate)
    {
        return = (from b in _appContext.TableName
                  select b
                  ).Where(predicate).Count();
    }

The same call worked:

    GetCount(p => p.Email == 'test@gmail.com');