[英]LINQ Join (Left Outer) with Take(1)
如果沒有任何地址(內部聯接),我將在下面的LINQ中返回零。 我如何將其設置為外部聯接,然后僅Take(1)
?
var results = query.Join(
DB.tblAddresses.Where(t => t.AddressTypeID == 'm' || t.AddressTypeID == 'b').OrderByDescending(x => x.AddressTypeID),
p => p.PersonID,
a => a.PersonID,
(p, a) =>
new
{
p.PersonID,
p.LastName,
p.FirstName,
p.MiddleName,
p.SSN,
p.BirthDate,
p.DeathDate,
AddressLine1 = a.AddressLine1 ?? string.Empty
});
return results.CopyLinqToDataTable();
使用GroupJoin :
var results = query.GroupJoin(
addresses,
p => p.PersonID,
a => a.PersonID,
(p, a) =>
new
{
p.PersonID,
p.LastName,
p.FirstName,
p.MiddleName,
p.SSN,
p.BirthDate,
p.DeathDate,
AddressLine1 = a.Any()
? (a.First().AddressLine1 ?? string.Empty)
: null
});
query
.SelectMany (
p => DB.tblAddresses.Where((t => t.AddressTypeID == 'm' || t.AddressTypeID == 'b') && t.PersonID == p.PersonID)**.DefaultIfEmpty()**,
(p, t) =>
new
{
p.PersonID,
p.LastName,
p.FirstName,
p.MiddleName,
p.SSN,
p.BirthDate,
p.DeathDate
Addressline1 = (t == null ? null : t.AddressLine1)
}
)
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