PM> Install-Package Canducci.Excel

//Setting the header
HeaderCollection headerData = new HeaderCollection();
headerData.Add(new Header("DateCreated", 1));

//Array
var n = new DateTime[] { DateTime.Now.Date.AddDays(-15), DateTime.Now.Date.AddDays(-16) };

//Using the extensive method to generate the file and write to disk.
n.ToExcelSaveAs("Result\\DatasSimples.xlsx", headerData);

int[,] c = new int[2,2];
c[0, 0] = 1; c[0, 1] = 2;
c[1, 0] = 3; c[1, 1] = 4;

//Setting the header
HeaderCollection headersArrayBi = new HeaderCollection();
headersArrayBi.Add(2, "Col-");

//Using the extensive method to generate the file and write to disk.
c.ToExcelSaveAs<int[,]>("Result\\ArrayBi2Dimensioanl.xlsx", headersArrayBi);

//Setting the header
HeaderCollection headers = new HeaderCollection();                  
headers.Add(new Header("Id", 1));
headers.Add(new Header("Nome", 2));
headers.Add(new Header("Valor", 3));
headers.Add(new Header("Data de Validade", 4));
headers.Add(new Header("Hora Stamp", 5));

//Manually creating a typed list
IList<Test> tests = new List<Test>();
tests.Add(new Test() { Id = 1, Nome = "Test 1", Valor = 10M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });
tests.Add(new Test() { Id = 2, Nome = "Test 2", Valor = 2000.69M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });
tests.Add(new Test() { Id = 3, Nome = "Test 3", Valor = 10M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });
tests.Add(new Test() { Id = 4, Nome = "Test 4", Valor = 20M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });
tests.Add(new Test() { Id = 5, Nome = "Test 5", Valor = 10M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });
tests.Add(new Test() { Id = 6, Nome = "Test 6", Valor = 2000.69M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });
tests.Add(new Test() { Id = 7, Nome = "Test 7", Valor = 10M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });
tests.Add(new Test() { Id = 8, Nome = "Test 8", Valor = 20M, 
            Data = DateTime.Now.Date, Time = DateTime.Now.TimeOfDay });

//Usando o método extensivo para gerar o arquivo e gravar em disco.
tests.ToExcelSaveAs("Result\\List.xlsx", headers);

using (AdventureWorks2014Entities db = new AdventureWorks2014Entities())
{

    //IQueryable<Person>   
    var Query = db.Person
            .AsNoTracking()
            .AsQueryable();
    
    //Setting the header
    HeaderCollection headerEF = new HeaderCollection();
    headerEF.Add(new Header("Primeiro Nome", 1));

    //Using the extensive method to generate the file and write to disk.    
    Query.Select(x => x.FirstName)                    
        .Take(10)
        .ToExcelSaveAs("Result\\Forma1.xlsx", headerEF);

}

[Route("excel")]
public FileContentResult CreateExcel()
{

    //Array de bytes
    byte[] fileByte = null;

    using (AdventureWorks2014Entities db = new AdventureWorks2014Entities())
    {

        //Setting the header
        HeaderCollection headers = HeaderCollection.Create();
        headers.Add(Header.Create("Id", 1));
        headers.Add(Header.Create("Sexo", 2));
        headers.Add(Header.Create("Data", 3));
        headers.Add(Header.Create("Trabalho", 4));

        //Using the Extensive Method to Generate an Array of Bytes in Memory
        //by the extensive method ToExcelByte
        fileByte = db.Employee
            .AsNoTracking()
            .Select(x => new
            {
                x.BusinessEntityID,
                x.Gender,
                x.HireDate,
                x.JobCandidate
            })                    
            .Take(20)
            .ToExcelByte(headers);

    }           
    
    //The browser will download the file
    return File(fileByte, ContentTypeExcel.Xlsx.ToValue(), "file.xlsx");

}

[Route("excel")]
public FileContentResult CreateExcel1()
{
    //Array of Bytes
    byte[] fileByte = null;

    //Entity Framework and MemoryStream
    using (AdventureWorks2014Entities db = new AdventureWorks2014Entities())
    using (System.IO.MemoryStream Stream = new System.IO.MemoryStream())            
    {
        //Setting the header
        HeaderCollection Headers = HeaderCollection.Create();
        Headers.Add(Header.Create("Departamento", 1));
        Headers.Add(Header.Create("Razão Social", 2));

        //Building Query and Returning an IQueryable
        IQueryable Query = db.Department.Select(x => new { x.DepartmentID, x.Name }).AsQueryable();

        //Instantiating the ListToExcel class
        IListToExcel<Department> listDep = new ListToExcel<Department>(Query, Headers);

        //SaveAs passing values ​​to the MemoryStream (`Stream`)
        listDep.SaveAs(Stream);

        //Assigning values ​​to Array of Bytes
        fileByte = Stream.ToArray();

    }

    //The browser will download the file
    return File(fileByte, ContentTypeExcel.Xlsx.ToValue(), "file.xlsx");

}

protected void BtnEnviar_Click(object sender, EventArgs e)
{
    var Items = new[]
    {
        new {Id  = 1, Name = "Id 1", Value = 150.00M},
        new {Id  = 2, Name = "Id 2", Value = 250.25M},
        new {Id  = 3, Name = "Id 3", Value = 450.00M}
    }.ToArray();

    byte[] ArrayOfBytes = Items.ToExcelByte();


    Response.ClearContent();
    Response.ClearHeaders();
    

    Response.AddHeader("content-disposition", "attachment; filename=file.xls");

    Response.ContentType = "application/ms-excel";

    Response.BinaryWrite(ArrayOfBytes);

    Response.End();
    
}

HeaderCollection Headers = HeaderCollection.Create();
Headers.Add(Header.Create("Departamento", 1));
Headers.Add(Header.Create("Razão Social", 2));