If the TotalWidth value is larger than the DataWidth value you have ECC memory.

CMD 

wmic MEMORYCHIP get DataWidth,TotalWidth

If the TotalWidth value is larger than the DataWidth value you have ECC memory.

Example output:

//ECC Memory
DataWidth  TotalWidth
64         72

//Non-ECC Memory
DataWidth  TotalWidth
64         64

Or

wmic memphysical get memoryerrorcorrection

wmic memphysical get memoryerrorcorrection
This will return a code based on the type of memory installed:
Value Meaning 
0 (0x0) Reserved 

1 (0x1) Other 

2 (0x2) Unknown 

3 (0x3) None 

4 (0x4) Parity 

5 (0x5) Single-bit ECC 

6 (0x6) Multi-bit ECC 

7 (0x7) CRC