Multiple 'Or' statements in EF expression

Question

Given a list of filter parameters in the form of:

public class filterParm
{
    public int age { get; set; }
    public string name { get; set; }
}

Where:

var parms = new List<filterParm>
{
    new filterParm {age = 22, "phil"},
    new filterParm {age = 19, "dave"},
    new filterParm {age = 31, "nick"}
};

How do I write an expression which would result in the following SQL where clause (note the OR operators in bold:

WHERE (age = 22 AND name = "phil")
OR (age = 19 AND name = "dave") OR (age = 31 AND name = "nick")

My current implementation results in each of the statements seperated by the AND operator:

private _dbSet<user> Users { get; set; }
public List<user> CustomFilter(List<filterParm> parms)
{
    IQueryable<TEntity> query = _dbSet;

    if (parms.Count > 0 )
    {
        foreach (var parm in parms)
        {                    
           query = query.Where(u => u.Age == parm.Age && u.Name == parm.Name);
        }
    }

    return query.ToList();
}

The code above results in the following SQL:

WHERE (age = 22 AND name = "phil") AND (age = 19 AND name = "dave") AND (age = 31 AND name = "nick")

What do I need to change in the expression to cause the generated SQL to use 'OR' instead of 'AND' in the indicated locations? I would prefer to avoid using third party libraries where possible.

EDIT: As suggested by @KingKing, a union does return the required results:

private _dbSet<user> Users { get; set; }
public List<user> CustomFilter(List<filterParm> parms)
{
    IQueryable<TEntity> query = _dbSet;

    if (parms.Count > 0)
    {
        query = query.Where(u => u.Age == parms[0].Age && u.Name == parms[0].Name);

        for (int i = 1; i < parms.Count; i++)
        {
            var parm = parms[i];
            query = query.Union(DbSet.Where(u => u.Age == parm.Age && u.Name == parm.Name));
        }                                                   
    }
    return query.ToList();
}

I would still like to know if it is possible to generate the statement using the 'Or' operator as described.

Answer 1

I think using Union will help:

public List<user> CustomFilter(List<filterParm> parms) {
  IQueryable<TEntity> query = _dbSet;
  if (parms.Count > 0 ){
    IQueryable<TEntity> init = _dbSet;
    var firstParm = parms[0];
    query = query.Where(u => u.Age == firstParm.Age && u.Name == firstParm.Name);
    for(int i = 1; i < parms.Count; i++)
    {                    
       var nextParm = parms[i];
       init = init.Where(u => u.Age == nextParm.Age && u.Name == nextParm.Name);
       query = query.Union(init);
    }
  }
  return query.ToList();
}