Update list object based on other LINQ / LAMBDA - c#-3.0

Question

Here are my two objects
public class ObjectHeaderBuffer
{
public int DataObjectId { get; set; }
public string FileName { get; set; }
public int RowCount { get; set; }
public string Checksum { get; set; }
public int ReconTarget { get; set; }
}
public class ObjectHeaderAttribute
{
public int DataObjectId { get; set; }
public int AttributeType { get; set; }
public int AttributeValue { get; set; }
}
var ohBuffer = new List<ObjectHeaderBuffer>();
var ohAttribute = new List<ObjectHeaderAttribute>();
I want to update ohBuffer.ReconTarget with ohAttribute.AttributeValue where ohBuffer.DataObjectId == ohAttribute.DataObjectId
what is linq or lambda of this?

Answer 1

You need to iterate each item in ohBuffer and look up the value in ohAttribute.
Assuming there is only one Attribute for each Buffer, this will work.
ohBuffer.ForEach(b => b.ReconTarget = ohAttribute
.SingleOrDefault(a => a.DataObjectId == b.DataObjectId).AttributeValue);
If the lookup returns null, you can either coalesce to a new object and take the default value
ohBuffer.ForEach(b => b.ReconTarget =
(ohAttribute.SingleOrDefault(a => a.DataObjectId == b.DataObjectId)
?? new ObjectHeaderAttribute())
.AttributeValue);
or you could just take null
ohBuffer.ForEach(b => b.ReconTarget =
{
var attribute = ohAttribute
.SingleOrDefault(a => a.DataObjectId == b.DataObjectId);
if (attribute == null)
return null;
return attribute.AttributeValue;
});

Answer 2

They way i did is:
foreach (var objectHeaderBuffer in ohBuffer)
{
var objectHeaderAttribute = (from c in ohAttribute where c.DataObjectId == objectHeaderBuffer.DataObjectId select c).First();
objectHeaderBuffer.ReconTarget = objectHeaderAttribute.AttributeValue;
}

Answer 3

If your relation is 1:1 Then
foreach (ObjectHeaderBuffer Itemx in ohBuffer)
{
ObjectHeaderAttribute Itemy= (from ObjectHeaderAttribute c in ohAttribute where c.DataObjectId == Itemx.DataObjectId select c).FirstOrDefault();
if(Itemy!=null)
{
Itemx .ReconTarget = Itemy.AttributeValue;
}
}
Or
foreach (ObjectHeaderBuffer Itemx in ohBuffer)
{
ObjectHeaderAttribute Itemy= ohAttribute.Where(c=>c.DataObjectId == Itemx .DataObjectId).FirstOrDefault();
if(Itemy!=null)
{
Itemx .ReconTarget = Itemy.AttributeValue;
}
}