LINQ with conditions that some columns could be ignored depends on user input?-CodePudding

I have TableA with 3 columns ColA, ColB, ColC. I'm developing a query function like the code shown below, because I want to make that if ValueB & ValueC are null, or string.Empty, then ColB, ColC may be not included in the query condition.....

IList<TableA> Query(object ValueA,string ValueB,string ValueC)
var result=(from TableA TA in entity.TableA
            where TA.ColA==ValueA
            &&(string.IsNullOrWhiteSpace(ValueB)?1==1:TA.ColB==ValueB)
            &&(string.IsNullOrWhiteSpace(ValueC)?1==1:TA.ColC==ValueC)
            select TA);

but I got a "System.NotSupportedException" exception while executed to this part:

string.IsNullOrWhiteSpace(ValueB)

Could someone guide me a right way to make it?

Sorry for being a Taiwanese so the error message I met contains Chinese words.

CodePudding user response：

Compose your query conditionally. Start with the base query:

var query = entity.TableA
    .Where(ta => ta.ColA == ValueA);

Then build upon the query when the other parameter values are not null or white space:

if(!string.IsNullOrWhitespace(ValueB))
{
    query = query.Where(ta => ta.ColB == ValueB);
}

CodePudding user response：

Instead of using string.IsNullOrWhiteSpace method. You can check like below

(ValueB == null || ValueB == "")