¿Cómo pasar un List<> (lista genérica) a un DataTable?

 Me tope con la necesidad de pasar una lista ó IEnumerable a un DataTable

public static DataTable LINQToDataTable<T>(IEnumerable<T> varlist)
        {
            DataTable dtReturn = new DataTable();
            PropertyInfo[] oProps = null;

            if (varlist == null) return dtReturn;
            foreach (T rec in varlist)
            {
                if (oProps == null)
                {
                    oProps = ((Type)rec.GetType()).GetProperties();
                    foreach (PropertyInfo pi in oProps)
                    {
                        Type colType = pi.PropertyType;
                        if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof(Nullable<>)))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }
                        dtReturn.Columns.Add(new
                        DataColumn(pi.Name, colType));
                    }
                }
                DataRow dr = dtReturn.NewRow();
                foreach (PropertyInfo pi in oProps)
                {
                    dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue(rec, null);
                }
                dtReturn.Rows.Add(dr);
            }
            return dtReturn;
        }

LINQ Group By y select collection c#

Objeto 

 items.GroupBy(item => item.Order.Customer)

     .Select(group => new { Customer = group.Key, Items = group.ToList() })
     .ToList();

Lista de enteros:

  List<int> solicitudes = partidasPAD.PartidaPAD.GroupBy(x => x.idSolicitud).Select(grupo => grupo.Key).ToList();

Convertir DataReader a DataTable C# (SqlDataReader to DataTable)

 Puede cargar un archivo DataTabledirectamente desde un lector de datos utilizando el Load()método que acepta un archivo IDataReader.

var dataReader = cmd.ExecuteReader();
var dataTable = new DataTable();
dataTable.Load(dataReader);

o

  var dataTable = new System.Data.DataTable();
   var dt = new System.Data.DataTable();

  SqlDataReader dr;

  dr = cmd.ExecuteReader();

 if (dr.Read())
                    {
                        dataTable.Load(dr);
                        dt = dataTable;
                    }

Error CS0051 Inconsistent accessibility: parameter type

Para Solucionar el problema es necesario buscar la clase o interfaz y agregar un modificador de acceso público 

Entity framework code-first null clave externa

 

public class User
{
    public int Id { get; set; }
    public int? CountryId { get; set; }
    public virtual Country Country { get; set; }
}

Could not load file or assembly 'Microsoft.ReportViewer.WebForms, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91' or one of its dependencie

He instalado Microsoft.ReportViewer.2012.Runtime nuget package y el problema se ha resuelto sin instalar ReportViewer.msi o sql feature pack 12

Could not load file or assembly 'DocumentFormat.OpenXml, Version=2.0.5022.0, Culture=neutral, PublicKeyToken = 31bf3856ad364e35 'o una de sus dependencias.

Solucion:

En su caso, instale la versión 2.5 de DocumentFormat.OpenXml disponible en este enlace de Microsoft

Problema al llamar a Get Method of a Rest API en la web en mi código Xamarin.Forms

 System.NullReferenceException: Object reference not set to an instance of an object.


Estoy tratando de consumir un método Get de un WebAPI aleatorio en la Web a través de mi Xamarin.Formscódigo. Pero no puedo llamar a esa API.

Codigo Inicial

  private HttpClient httpClient;  

  public async Task<List<User>> GetUsersGroup(string group)

        {          

            List<User> users1 = new List<User>();

            var url = $"{Config.RoomsEndPoint}/{group}";

            var result = await httpClient.GetStringAsync(url);

            users1 = JsonConvert.DeserializeObject<List<User>>(result);

            return users1;

        }

Solucion

private HttpClient httpClient; 

public async Task<List<User>> GetUsersGroup(string group)

        {

            if (httpClient == null)

            {

                httpClient = new HttpClient();

            }

            List<User> users1 = new List<User>();

            var url = $"{Config.RoomsEndPoint}/{group}";

            var result = await httpClient.GetStringAsync(url);

            users1 = JsonConvert.DeserializeObject<List<User>>(result);

            return users1;

        }

Error: unexpected element found in XAMARIN

De repente recibo este error de compilación en VS 2019 pero no en VS 2017 cuando construyo mi proyecto de Android:
unexpected element <receiver> found in <manifest>
Solución:

entrar a las opciones del proyecto android y marcar la propiedad Use Incremental Android packaging system (aapt2)

Despues compilar
volver a entrar a esa opcion y desmarcar.

Compilar, y ya no debe marcar ese error.

Exportar Lista Objeto a Excel C#

public void ExportToExcel<T>(List<T> list)

    {

        int columnCount = 0;

        DateTime StartTime = DateTime.Now;

        StringBuilder rowData = new StringBuilder();

        PropertyInfo[] properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);

        rowData.Append("<Row ss:StyleID=\"s62\">");

        foreach (PropertyInfo p in properties)

        {

            if (p.PropertyType.Name != "EntityCollection`1" && p.PropertyType.Name != "EntityReference`1" && p.PropertyType.Name != p.Name)

            {

                columnCount++;

                rowData.Append("<Cell><Data ss:Type=\"String\">" + p.Name + "</Data></Cell>");

            }

            else

                break;

        }

        rowData.Append("</Row>");

        foreach (T item in list)

        {

            rowData.Append("<Row>");

            for (int x = 0; x < columnCount; x++) //each (PropertyInfo p in properties)

            {

                object o = properties[x].GetValue(item, null);

                string value = o == null ? "" : o.ToString();

                rowData.Append("<Cell><Data ss:Type=\"String\">" + value + "</Data></Cell>");

            }

            rowData.Append("</Row>");

        }

        var sheet = @"<?xml version=""1.0""?>

<?mso-application progid=""Excel.Sheet""?>

<Workbook xmlns=""urn:schemas-microsoft-com:office:spreadsheet""

xmlns:o=""urn:schemas-microsoft-com:office:office""

xmlns:x=""urn:schemas-microsoft-com:office:excel""

xmlns:ss=""urn:schemas-microsoft-com:office:spreadsheet""

xmlns:html=""http://www.w3.org/TR/REC-html40"">

<DocumentProperties xmlns=""urn:schemas-microsoft-com:office:office"">

<Author>MSADMIN</Author>

<LastAuthor>MSADMIN</LastAuthor>

<Created>2011-07-12T23:40:11Z</Created>

<Company>Microsoft</Company>

<Version>12.00</Version>

</DocumentProperties>

<ExcelWorkbook xmlns=""urn:schemas-microsoft-com:office:excel"">

<WindowHeight>6600</WindowHeight>

<WindowWidth>12255</WindowWidth>

<WindowTopX>0</WindowTopX>

<WindowTopY>60</WindowTopY>

<ProtectStructure>False</ProtectStructure>

<ProtectWindows>False</ProtectWindows>

</ExcelWorkbook>

<Styles>

<Style ss:ID=""Default"" ss:Name=""Normal"">

<Alignment ss:Vertical=""Bottom""/>

<Borders/>

<Font ss:FontName=""Calibri"" x:Family=""Swiss"" ss:Size=""11"" ss:Color=""#000000""/>

<Interior/>

<NumberFormat/>

<Protection/>

</Style>

<Style ss:ID=""s62"">

<Font ss:FontName=""Calibri"" x:Family=""Swiss"" ss:Size=""11"" ss:Color=""#000000""

ss:Bold=""1""/>

</Style>

</Styles>

<Worksheet ss:Name=""Sheet1"">

<Table ss:ExpandedColumnCount=""" + (properties.Count() + 1) + @""" ss:ExpandedRowCount=""" + (list.Count() + 1) + @""" x:FullColumns=""1""

x:FullRows=""1"" ss:DefaultRowHeight=""15"">

" + rowData.ToString() + @"

</Table>

<WorksheetOptions xmlns=""urn:schemas-microsoft-com:office:excel"">

<PageSetup>

<Header x:Margin=""0.3""/>

<Footer x:Margin=""0.3""/>

<PageMargins x:Bottom=""0.75"" x:Left=""0.7"" x:Right=""0.7"" x:Top=""0.75""/>

</PageSetup>

<Print>

<ValidPrinterInfo/>

<HorizontalResolution>300</HorizontalResolution>

<VerticalResolution>300</VerticalResolution>

</Print>

<Selected/>

<Panes>

<Pane>

<Number>3</Number>

<ActiveCol>2</ActiveCol>

</Pane>

</Panes>

<ProtectObjects>False</ProtectObjects>

<ProtectScenarios>False</ProtectScenarios>

</WorksheetOptions>

</Worksheet>

<Worksheet ss:Name=""Sheet2"">

<Table ss:ExpandedColumnCount=""1"" ss:ExpandedRowCount=""1"" x:FullColumns=""1""

x:FullRows=""1"" ss:DefaultRowHeight=""15"">

</Table>

<WorksheetOptions xmlns=""urn:schemas-microsoft-com:office:excel"">

<PageSetup>

<Header x:Margin=""0.3""/>

<Footer x:Margin=""0.3""/>

<PageMargins x:Bottom=""0.75"" x:Left=""0.7"" x:Right=""0.7"" x:Top=""0.75""/>

</PageSetup>

<ProtectObjects>False</ProtectObjects>

<ProtectScenarios>False</ProtectScenarios>

</WorksheetOptions>

</Worksheet>

<Worksheet ss:Name=""Sheet3"">

<Table ss:ExpandedColumnCount=""1"" ss:ExpandedRowCount=""1"" x:FullColumns=""1""

x:FullRows=""1"" ss:DefaultRowHeight=""15"">

</Table>

<WorksheetOptions xmlns=""urn:schemas-microsoft-com:office:excel"">

<PageSetup>

<Header x:Margin=""0.3""/>

<Footer x:Margin=""0.3""/>

<PageMargins x:Bottom=""0.75"" x:Left=""0.7"" x:Right=""0.7"" x:Top=""0.75""/>

</PageSetup>

<ProtectObjects>False</ProtectObjects>

<ProtectScenarios>False</ProtectScenarios>

</WorksheetOptions>

</Worksheet>

</Workbook>";

        System.Diagnostics.Debug.Print(StartTime.ToString() + " - " + DateTime.Now);

        System.Diagnostics.Debug.Print((DateTime.Now - StartTime).ToString());

        string attachment = "attachment; filename=Report.xml";

        HttpContext.Current.Response.ClearContent();

        HttpContext.Current.Response.AddHeader("content-disposition", attachment);

        HttpContext.Current.Response.Write(sheet);

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

        HttpContext.Current.Response.End();

    }

USO DEL METODO:

  ExportToExcel(TuLista);