将两个 LINQ 查询转换为单个查询

Question

I have made two LINQ queries one for getting Id and another for getting amount from the same model class. Since I am new to LINQ I don't know whether these two queries can be combined and get the same result.

var KID = db.Nikashas.Where(n => n.NIKASHAId == id).Select(n => n.KaryakramId).FirstOrDefault();
var KAMT = db.Nikashas.Where(n => n.NIKASHAId == id).Select(n => n.NikashaAmount).FirstOrDefault();
int kid = Convert.ToInt32(KID);
decimal kamt = Convert.ToDecimal(KAMT);

Both the above queries give the same row only selected fields are different. So is there any way I can use one single query to retrieve both the values and then how to convert KaryakramId to int and NikashaAmount to decimal ?

Answer 1

You can use projection and assign it on anonymous type:

var KID = db.Nikashas.Where(n => n.NIKASHAId == id).Select(n => new { karya = n.KaryakramId, nika = n.NikashaAmount }).FirstOrDefault();

Then from there you can access it via properties of your anonymous type:

int kid = Convert.ToInt32(KID.karya);
decimal kamt = Convert.ToDecimal(KID.nika);

Answer 2

The required data can be accessed with FirstOrDefault() extension and assign to anonymous type as:

var result = db.Nikashas
              .FirstOrDefault()(n => n.NIKASHAId == id)
              .Select(n => new 
               { 
                  kId = n.KaryakramId,
                  kAmt = n.NikashaAmount 
               });

From the result , required values can be accessed from anonymous type:

int kid = Convert.ToInt32(result.kId);
decimal kamt = Convert.ToDecimal(result.kAmt);

Answer 3

You could do something like this, assuming that your values are returned as strings and will be valid when converted to their types, and that the nikasha object is not too big that returning the whole thing adversely affects performance:

var nikasha = db.Nikashas.Where(n => n.NIKASHAId == id).FirstOrDefault();

//to handle a default null, check for null
if(nikasha != null)
{
    int KID = int.Parse(nikasha.KaryakramId);
    decimal KAMT = decimal.Parse(nikasha.NikashaAmount);
}

Answer 4

var res = db.Nikashas.Where(n => n.NIKASHAId == id)
    .Select(n => new { 
        kid = Convert.ToInt32(n.KaryakramId),  
        kamt = Convert.ToDecimal(n.NikashaAmount)}).FirstOrDefault();

int kid = res.kid;
decimal kamt = res.kamt;

Answer 5

You can use select new object with some property that you want

var result = db.Nikashas.Where(n => n.NIKASHAId == id).Select(n => new { n.KaryakramId, n.NikashaAmount}).FirstOrDefault();