How to use Temp table as data source of form in AX 2012

Yes, you can use temporary table as datasource whether it is of type tempDb or InMemory.

I assumed that you have temporary table ready and just need to drag in to the form datasource.

Now, Create one method named insertRecords at form level.

eg.,

TmpTable insertRecords()
{

TmpTable tmpTableBuffer;
OtherTable otherTableBuffer;

while tmpTableBuffer
{
tmpTableBuffer.field1 = otherTableBuffer.field1;
.
.
.
.
.
tmpTableBuffer.fieldn = otherTableBuffer.fieldn;
tmpTableBuffer.insert();
}

Now, call this method in init method of form after super.

public void init()
{

super();

// important thing comes here
// if table is of type InMemory,call following method.

TmpTable.setTmpData(element.insertRecords());

// if table is of type tempDb, call following method.

TmpTable.linkPhysicalTableInstance(element.insertRecords());
}