Linq - Select a particular column

Question

In Table I have 5 columns :- name, age, dob, doj, entrydate.

string column = 'dob'; // This is dynamic

var data = ctx.tblTable
                    .Where(e => e.Id == Id && e.Name == name)
                    .Select(e => column).SingleOrDefault();

Unfortunately, this doesn't work. How to select a particular column in linq.

I don't know for sure, but I think you'll have to pull the full row down, then use reflection to grab the individual column. I like to think there's a better way, but that's the best one I know of. — Matthew Haugen, Oct 06 '14 at 07:33
Perhaps this answer can help you too: http://stackoverflow.com/a/233505/858757 — Silvermind, Oct 06 '14 at 08:17

score 3 · Answer 1 · answered Oct 06 '14 at 07:31

3

Use as

var data = ctx.tblTable
                .Where(e => e.Id == Id && e.Name == name)
                .SingleOrDefault().ColumnName;

answered Oct 06 '14 at 07:31

Amit

14,671
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Arun Ghosh · Accepted Answer · 2014-10-06T08:30:02.833

3

string column = 'dob'; // This is dynamic

var data = ctx.tblTable
                    .Where(e => e.Id == Id && e.Name == name)
                    .ToList()
                    .Select(e => GetPropValue(e, column))
                    .FirstOrDefault();


public object GetPropValue(object obj, string propName)
{
     return obj.GetType().GetProperty(propName).GetValue(obj, null);
}

edited Oct 06 '14 at 08:30

answered Oct 06 '14 at 07:38

Arun Ghosh

6,820
1
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I get this Error :- `{"LINQ to Entities does not recognize the method 'System.Object GetPropValue(System.Object, System.String)' method, and this method cannot be translated into a store expression."}` – Anup Oct 06 '14 at 08:28
This will pull the entire table in memory first – jeroenh Oct 06 '14 at 08:36
@jeroenh No. It will pull only the table entries matching query **Where(e => e.Id == Id && e.Name == name)** – Arun Ghosh Oct 06 '14 at 08:58

G J · Answer 3 · 2014-10-06T07:41:49.197

0

You can try

string column = 'dob';
var data = ctx.tblTable
                .Where(e => e.Id == Id && e.Name == name)
                .Select(e = > e.GetType().GetProperty(column).GetValue(e,null));

edited Oct 06 '14 at 07:41

answered Oct 06 '14 at 07:31

G J

446
8
20

score 0 · Answer 4 · answered Oct 06 '14 at 08:13

Use a SQL query instead? I assume that you are using Entity Framework. In that case use:

var columnValues = ctx.Database
         .SqlQuery<string>("SELECT " + column + " FROM tblTable WHERE Id = " + Id + " AND Name = '" + name + "'").ToList();

And make sure that column, Id and name do not allow SQL injection or unwanted values. You could do that with parametrized queries.

score 0 · Answer 5 · answered Oct 06 '14 at 13:55

public class TestClass
    {
        public Guid Id { get; set; }
        public string Name { get; set; }
        public DateTime Dob { get; set; }

        public void YourMethod()
        {
            List<TestClass> temp = new List<TestClass>();

            var x = from xyz in temp
                    where xyz.Name == "Name" && xyz.Id == new Guid()
                    select xyz.Dob;
        }
    }

Linq - Select a particular column

5 Answers5