How do you write a parameterized where-in raw sql query in Entity Framework

Here's how you would write your query in SQL.

select *
    from MyTable
    where dateColumn in ('2014-01-01', '2014-02-01', '2014-03-01')

So one shall not expect otherwise than having to represent this string entirely delimited by parenthesis.

var dateQueryString = string.Join(",", chartModelData.GetFormattedDateList());
// Dates shall be returned as DateTime.ToShortDateTimeString() as follows:
// '2014-01-01', '2014-02-01', '2014-03-01'

Then only remains to wrap it in parenthesis.

var sql = @"select max(data_seq)    as MaxSeq
                    , min(data_seq) as MinSeq
                    , count(1)      as TotSampleCnt
                from spcdata_tb
                where data_wadate in (@DateParam)
                    and line_code  =  @LineCode
                    and model_no   =  @ModelNumber
                    and lot_no     =  @LotNumber
                    and equip_no like @EquipNumber";

Provide the parameters values for each named parameter, and voilà! This shall do it!

This isn't a problem specific to entity-framework, you can solve it by generating your own parameter names dynamically.

var parameters = new List<SqlParameter> {
    new SqlParameter("@DateParam", dateQueryString),
    new SqlParameter("@LineCode", chartModelData.LineCode),
    new SqlParameter("@ModelNumber", chartModelData.ModelNum),
    new SqlParameter("@EquipNumber", equipmentNumber),
    new SqlParameter("@LotNumber", chartModelData.LotNum)   
};

var dateParameters = chartModelData
    .GetFormattedDateList()
    .Select((date, index) => new SqlParameter("@date" + index, date));
    .ToList();

parameters.AddRange(dateParameters);
    
var inValues = string.Join(", ", dateParameters.Select(p => p.ParameterName));

var query = @"SELECT MAX(DATA_SEQ) AS MaxSeq, 
   MIN(DATA_SEQ) AS MinSeq, 
   COUNT(1) AS TotSampleCnt
   FROM SPCDATA_TB
   WHERE DATA_WDATE IN (" + inValues + @")  
   AND LINE_CODE = @LineCode
   AND MODEL_NO = @ModelNumber
   AND LOT_NO = @LotNumber
   AND EQUIP_NO LIKE @EquipNumber";

var myResult = _dbContext.Database
    .SqlQuery<SPCDataSeqCntInfo>(query, parameters.ToArray());

The resulting query sent to SQL-Server will look like the following:

SELECT 
   MAX(DATA_SEQ) AS MaxSeq, 
   MIN(DATA_SEQ) AS MinSeq, 
   COUNT(1) AS TotSampleCnt
FROM SPCDATA_TB
WHERE DATA_WDATE IN (@date0, @date1, @date2)  
AND LINE_CODE = @LineCode
AND MODEL_NO = @ModelNumber
AND LOT_NO = @LotNumber
AND EQUIP_NO LIKE @EquipNumber

Generally, you want to avoid doing string manipulation when writing queries, however, I believe this example is safe from sql-injection.