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.

Answer 1

Use as

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

Answer 2

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);
}

Answer 3

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));

Answer 4

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.

Answer 5

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;
        }
    }