The handling method that failed to convert the LINQ string to datetime

Today, when using LINQ, since the time saved in the database is in varchar() format, it is necessary to compare the time order when querying, so it USES:

from j in system.jhzd
where j.dwbm.ToString().Trim() == branchcode.ToString().Trim()
&& Convert.ToDateTime(j.yearmonth.ToString().Trim()).CompareTo(Convert.ToDateTime(timeFrom)) >= 0
&& Convert.ToDateTime(j.yearmonth.ToString().Trim()).CompareTo(Convert.ToDateTime(timeTo)) <= 0
join b in system.t_sys_Branch
on j.dwbm.ToString().Trim() equals b.BranchCode
join c in system.T_CWLB
on j.xmlb.ToString().Trim() equals c.ID
select new
{
BranchName = b.BranchName,
category = c.CWMC,
money = j.je,
comefrom = j.zjly,
time = j.yearmonth,
zhaiyao = j.zhaiyao,
}

However, the database report "failed to convert from string to datetime" was found when used.

I tried a lot of things, but it didn't work. Finally, I found that the string in the yearmonth field in the database was "January 04, 2013".

When you change it to "2013-01-04", the query is found to be normal and valid.