Adding conditions in dynamic linq

Question

I want to write a dynamic linq query that checks for 'where' condition based on two time frames, startTime and errorTime. The present code is here,

IQueryable<LogFormat> errorLines = null;
if (!string.IsNullOrEmpty(errorStartTime) && !string.IsNullOrEmpty(errorTime))
{
    var sTime = DateTime.Parse(errorStartTime);
    var eTime = DateTime.Parse(errorTime);
    errorLines = from errorLine in File
                 where
                     (errorLine.DateTime >= sTime && errorLine.DateTime <= eTime) &&
                     (
                     errorLine.Level == "ERR"
                     || errorLine.Level == "WARN"
                     )
                 select errorLine;
}
else if (!string.IsNullOrEmpty(errorStartTime))
{
    var sTime = DateTime.Parse(errorStartTime);
    errorLines = from errorLine in File
                 where
                     errorLine.DateTime >= sTime
                     &&
                     (
                     errorLine.Level == "ERR"
                     || errorLine.Level == "WARN"

                     )
                 select errorLine;

}
else if (!string.IsNullOrEmpty(errorTime))
{
    var eTime = DateTime.Parse(errorTime);

    errorLines = from errorLine in File
                 where
                     errorLine.DateTime <= eTime
                     &&
                     (
                     errorLine.Level == "ERR"
                     || errorLine.Level == "WARN"
                   )
                 select errorLine;

}
else
{   
    errorLines = from errorLine in File
                 where
                     errorLine.Level == "ERR"
                     || errorLine.Level == "WARN"


                 select errorLine;

}

Can I know how to have just one query so that I can send start time and errortime dynamically to get the results?

cuongle · Accepted Answer · 2012-10-31 10:47:37Z

2

You can make it dynamic by calling the where clause multiple times, based on conditions:

var errorLines = File.Where(e => e.Level == "ERR" 
                              || e.Level == "WARN");                   

if (!string.IsNullOrEmpty(errorStartTime))
{
     var sTime = DateTime.Parse(errorStartTime);
     errorLines = errorLines.Where(e => e.DateTime >= sTime);
}

if (!string.IsNullOrEmpty(errorTime))
{
    var eTime = DateTime.Parse(errorTime);
    errorLines = errorLines.Where(e => e.DateTime <= eTime);
}

edited Oct 31, 2012 at 10:47

answered Oct 31, 2012 at 2:40

cuongle

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Comments

bor1s · Accepted Answer · 2012-10-31 10:41:06Z

0

You can dynamically build predicate and combine with And() Or() in using PredicateBuilder. Take a look at : http://www.albahari.com/nutshell/predicatebuilder.aspx

answered Oct 31, 2012 at 10:41

bor1s

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