Multi-conditional query _linq in LINQ

Multi-Criteria query in LINQ:

from S in data4
Join D1 in Data_co on new {S.forecasttime,s.regioncode}

equals new {D1. Monidate, D1. Regioncode}
But this only implements a join association, and an error occurs when there are multiple joins.

Modified as follows: Join D1 in Data_co on S.forecasttime equals D1. Monidate
where S.REGIONCODE==D1. Regioncode

An association that implements multiple join multiple conditions

var data7 = (from S in data4
Join D1 in Data_co on S.forecasttime equals D1. Monidate
where S.REGIONCODE==D1. Regioncode
Join D2 in Data_no2 on S.forecasttime equals D2. Monidate
where S.regioncode = = D2. Regioncode
Join D3 in Data_so2 on S.forecasttime equals D3. Monidate
where S.regioncode = = D3. Regioncode
Join D4 in Data_o3 on S.forecasttime equals D4. Monidate
where S.regioncode = = D4. Regioncode
Join D5 in data_o38h on S.forecasttime equals D5. Monidate
where S.regioncode = = d5. Regioncode
Join D6 in Data_pm10 on S.forecasttime equals D6. Monidate
where S.regioncode = = d6. Regioncode
Join D7 in DATA_PM25 on S.forecasttime equals D7. Monidate
where S.regioncode = = D7. Regioncode
Select New
{
Regioncode = S.regioncode,
Forecasttime = S.forecasttime,
Regionname = S.regionname,
CO = (decimal) d1.co,
NO2 = (short) d2. NO2,
SO2 = (short) D3. SO2,
O3 = (short) D4. O3,
o38h = (short) d5. O38H,
PM10 = (short) d6. PM10,
PM25 = (short) D7. PM25
}). (a => A.regioncode);