The entity type List`1 is not part of the model for the current context

where db is List

db.Entry(bd).State = EntityState.Modified;

DbContext.Entry(object) expects a single object, not a collection.
so use a loop instead

foreach (var item in bd)
{
    db.Entry(item).State = EntityState.Modified;
}

LINQ to Entities returning “Object reference not set to an instance of an object.”

EF does not support nullable composite primary keys if your one of the keys is null it will return the exception

How to store string in a cookie and retrieve it

Writing a cookie

HttpCookie myCookie = new HttpCookie("MyTestCookie");
DateTime now = DateTime.Now;
 
// Set the cookie value.
myCookie.Value = now.ToString();
// Set the cookie expiration date.
myCookie.Expires = now.AddYears(50); // For a cookie to effectively never expire
 
// Add the cookie.
Response.Cookies.Add(myCookie);

Reading a cookie

HttpCookie myCookie = Request.Cookies["MyTestCookie"];
 
// Read the cookie information and display it.
if (myCookie != null)
    Response.Write("<p>" + myCookie.Name + "<p>" + myCookie.Value);
else
    Response.Write("not found");

why cookies are always null after postback

private static string GetCookie(string name)
{
    return HttpContext.Current.Request != null ? HttpContext.Current.Request.Cookies[name].Value : string.Empty;
}
 
private static void SetCookie(string name, string value)
{
    HttpContext.Current.Request.Cookies[name].Value = value;
    HttpContext.Current.Request.Cookies[name].Expires = DateTime.Now.AddDays(100);
}

Could not find a row that matches the given keys in the original values stored in ViewState.

Add DataKeyNames="PrimaryKey1,PrimaryKey2,PrimaryKey3,....." to formview, gridview and/or listview

How to get sql server bak file logical name

RESTORE FILELISTONLY 
FROM  DISK = N'path to bak file' 
WITH  FILE = 1 
GO

Use WITH MOVE to identify a valid location for the file.

USE [master]
GO
RESTORE DATABASE [DBName] 
FROM  DISK = N'Path to BAK File' 
WITH  FILE = 1,  
MOVE N'Logical File Name' TO N'New Path to mdf file',  
MOVE N'Logical File Log Name' TO N'New Path to log file',  
NOUNLOAD,  REPLACE,  STATS = 1
GO

To get logical file list

RESTORE FILELISTONLY 
FROM  DISK = N'path to bak file' 
WITH  FILE = 1 
GO

crystal report for visual studio 2015 / dot net framework 4.6

just copy existing framework folder in aspnet_client\system_web folder and the rename it to 4_81 or whatever version you have installed and your are done
To Check your version click here
http://w3dproblems.dcense.com/2015/09/what-net-version-are-you-running-20-45.html

Binding to Navigation Property causes “ A field or property with the name 'X.X' was not found on the selected data source”

Replace asp:BoundField to asp:TemplateField

LINQ: SqlDateTime overflow. Must be between ...

WHEN a NULL value to passed to a non null datetime field using LINQ datasource. If the field is autogenerated make sure to mark as autogenerated in LINQ DBML designer else pass the value using a parameter

Get all asp net listview items in array

var rows = [];
$('#<%: lvStudents.ClientID %>_itemPlaceholderContainer tr:gt(1)').each(function (i, v) {
    var row = $(this);
    rows.push(row);
});

if InsertItemPosition="LastItem"
gt(1)
else if InsertItemPosition="FirstItem" 
gt(2)

How to update rows randomly

update dbo.Table 
set Field = Value 
where Id in ( select top 50 percent id from dbo.Table order by NEWID() )

Handling Multiple FULL OUTER JOIN in sql

SELECT A.column2 , B.column2 , C.column2 FROM ( 
 (SELECT month, column2 FROM table1) 
A 
 FULL OUTER JOIN 
 (SELECT month, column2 FROM table2) 
B on A.month= B.month 
 FULL OUTER JOIN 
 (SELECT month, column2 FROM table3) 
C on ISNULL(A.month, B.month) = C.month )

How to update rows with a random date

UPDATE table SET datetimecol = DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)

How to convert IList to IQuerable

IQueryable query = new List() { 1, 2, 3, 4, 5}.AsQueryable();

How to check if IQueryable result set is null or empty

list will never be null with LINQ; it will simply represent an "empty collection" if need be. The way to test is with the Any extension method:
if (list.Any()) 
{
// list has at least one item
}

Value cannot be null. Parameter name: panelsCreated[0] asp net

Switch scriptmanager mode to release

<asp:ScriptManager runat="server" ScriptMode="Release" />

InvalidOperationException: Could not find UpdatePanel with ID asp net

Change ClientIDMode on UpdatePanels to AutoID

<asp:UpdatePanel runat="server" ClientIDMode="AutoID">

How to use IndexOf() method of List <object> asp net c#

var index = students.FindIndex(st => st.ID == student.ID);

Using DataBinder.Eval in the RowDataBound Event asp net gridview

decimal totalAmount = 0;
protected void gv_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
 totalAmount += Decimal.Parse(DataBinder.Eval(e.Row.DataItem, "Amount").ToString());
}
}