Failed to convert from string to datetime

When using LINQ today, because the time in the database is saved in the varchar () format, the query time needs to be compared, so we use:

 

 
From J in system. jhzdwhere 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_branchon J. dwbm. tostring (). trim () equals B. branchcodejoin C in system. t_cwlbon J. xmlb. tostring (). trim () equals C. idselect new {branchname = B. branchname, Category = C. CWMC, money = J. je, comefrom = J. zjly, time = J. yearmonth, zhaiyao = J. zhaiyao ,}
 

However, database reports are discovered during use. "Failed to convert from string to datetime".

 

I tried a lot of methods and still didn't use them. I finally found that the string of the yearmonth field in the database is"January 04, 2013",

When you change it to "", the query is normal and valid.