Issue while performing Union on two sequences using Linq

Thanks for your help.I was able to solve the issue.

Please check below points:

1. Make sure the property names and types in both anonymous types match exactly.Even a slight difference in property names or types can cause this issue.

2. To avoid this issue is to use a named type (a class) instead of anonymous types. This ensures that both sequences have the same type.

3. If you want to continue using anonymous types, you can explicitly cast both sequences to a common type using the Select method.

Hello Hari Mone,

Have you verified the SELECT statement in both queries? They must have the same number of columns, with each column having the same data type.

Example : 

var sequence1 = someQueryable.Select(x => new CustomType 
{
    Id = x.Id,
    Name = x.Name ?? string.Empty  // Handle null for string property
}).AsEnumerable(); // Ensure it's IEnumerable

var sequence2 = anotherQueryable.Select(x => new CustomType 
{
    Id = x.Id,
    Name = x.Name ?? string.Empty
}).AsEnumerable();


// Union of both result set
var result = sequence1.Union(sequence2);

Hi Hari,

As the error mentioned, "There is a type mismatch between the two sequences while union". You must verify the types of each data member or you can use the approach like project/map into a named type and then apply the union. Here is an emaple code which you can use accordingly.

public class CustomType
{
    public int Id { get; set; }
    public string Name { get; set; }
    // Add other properties as needed
}

var firstQuery = from a in db.Table1
                    select new CustomType
                    {
                        Id = a.Id,
                        Name = a.Name,
						// Other Properties
                    };

var secondQuery = from b in db.Table2
                     select new CustomType
                     {
                        Id = b.Id,
                        Name = b.Name,
                        // Other Properties
                     };

var unionResult = firstQuery.Union(secondQuery).ToList();