//public static EntityQuery BuildQuery(IEntity entity, NavigationProperty np) {
// var ekQuery = BuildQuery(entity.EntityAspect.EntityKey);
// var q = ekQuery.ExpandNonGeneric(np.Name);
// return q;
//}
/// <summary>
/// Builds an <see cref="EntityQuery"/> to load the entities for the navigation property of the entity.
/// </summary>
public static EntityQuery BuildQuery(IEntity entity, NavigationProperty np)
{
if (np.IsScalar)
{
if (np.ForeignKeyNames.Count == 0)
{
return(null);
}
var relatedKeyValues = np.ForeignKeyNames.Select(fk => entity.EntityAspect.GetValue(fk)).ToArray();
var entityKey = new EntityKey(np.EntityType, relatedKeyValues);
return(BuildQuery(entityKey));
}
else
{
var inverseNp = np.Inverse;
var fkNames = inverseNp != null ? inverseNp.ForeignKeyNames : np.InvForeignKeyNames;
if (fkNames.Count == 0)
{
return(null);
}
var keyValues = entity.EntityAspect.EntityKey.Values;
var parameterExpr = Expression.Parameter(np.EntityType.ClrType, "t");
var propExpressions = fkNames.Select(name => Expression.Property(parameterExpr, name));
var fkExpression = BuildMultiEqualExpr(propExpressions, keyValues);
var entityQuery = EntityQuery.Create(np.EntityType.ClrType);
var queryLambda = Expression.Lambda(fkExpression, parameterExpr);
return(AddWhereClause(entityQuery, queryLambda));
}
}
/// <summary>
/// Returns a query that will return an Empty enumeration of specified type when executed.
/// </summary>
/// <param name="entityType"></param>
/// <returns></returns>
public static EntityQuery BuildEmptyQuery(Type entityType)
{
var parameterExpr = Expression.Parameter(entityType, "t");
// where 1 = 0;
var predicateExpr = Expression.Equal(Expression.Constant(1), Expression.Constant(0));
var lambdaExpr = Expression.Lambda(predicateExpr, parameterExpr);
var entityQuery = EntityQuery.Create(entityType);
entityQuery = AddWhereClause(entityQuery, lambdaExpr);
return(entityQuery);
}
/// <summary>
/// Builds an <see cref="EntityQuery"/> based on a collection of <see cref="EntityKey"/>s.
/// The EntityQuery returned is actually an EntityQuery{T} but T is unknown at compile time.
/// </summary>
/// <param name="keys"></param>
/// <returns></returns>
public static EntityQuery BuildQuery(IEnumerable <EntityKey> keys)
{
if (!keys.AllEqual(k => k.EntityType))
{
throw new ArgumentException("The EntityQueryBuilder.BuildQuery method requires that the 'keys' parameter consist of EntityKeys all with the same EntityType.");
}
var firstKey = keys.FirstOrDefault();
if (firstKey == null)
{
return(null);
}
var entityQuery = EntityQuery.Create(firstKey.EntityType.ClrType);
return(AddWhereClause(entityQuery, keys));
}