C#

1. Explanation of DBNull:This class is used to indicate that no known value exists (usually in database applications ).In database applications, empty objects are valid values of fields. This class distinguishes between null values (empty objects)

When C # is used to read text files, if it contains Chinese characters, garbled characters often occur. The general solution is to add an Encoding in StreamReader. I am using Encoding. UTF8. Generally, this parameter can be used. However, this time

Susing System. Net;Using System. IO;Using System. Text;// Method 1:// Create a request for the URL. WebRequest request = WebRequest. Create ("http://www.hao123.com /");// If required by the server, set the credentials.Request. Credentials =

Make an input interface today. There is a need to select a different one based on a DropDownList. Different Input interfaces are displayed in the following sections. If you place the RESPONSE event on the server, you must frequently click the page.

When writing code today, I was lazy and used dynamic. As a result, I encountered a problem and I was unable to get the attributes of the dynamic object at runtime. The original problem is simplified as follows: Assembly A contains the SampleClass

There are many methods to obtain the path in c #, which are generally used in the following five ways:   // Obtain the current working directory of the application. String path1 = System. IO. Directory. GetCurrentDirectory (); MessageBox. Show ("Get

Internal class Win32API{# Region Win32 API Interfaces[DllImport ("netapi32.dll", EntryPoint = "NetApiBufferFree")]Internal static extern void NetApiBufferFree (IntPtr bufptr );[DllImport ("netapi32.dll", EntryPoint =

The OleDbConnection. GetOleDbSchemaTable method can be used to obtain the Architecture Information of the data source to be retrieved. It is usually used as follows: DataTable Schemadt = OleDbConnection. GetOleDbSchemaTable (OleDbSchemaGuid. Tables,

Before. Net 4.0, in order to make search engine-friendly and user-friendly URLs, We need to rewrite the URLs by ourselves. Now we don't need it. Net 4.0 is doing this for us. UrlRouting is called Routing because it not only implements Url rewriting,

First paste the code Private bool isMouseDown = false;Private Point mouseOffset; // records the coordinates of the mouse pointer. Private void PicBox_MouseDown (object sender, MouseEventArgs e){If (e. Button = MouseButtons. Left){MouseOffset. X = e.

Compile and execute code at runtime. As shown below.   Open button to Open any text file and load it to TextBox. It can be changed after loading. Compile and execute the Compile button. The Code is as follows.    Code Code highlighting produced

1. DateTime numeric typeSystem. DateTime currentTime = new System. DateTime ();1.1 take the current year, month, day, hour, minute, secondCurrentTime = System. DateTime. Now;1.2 get current yearInt Year = currentTime. Year;1.3 take the current

1 btn Button2 chk CheckBox3 ckl CheckedListBox4 cmb ComboBox5 dtp DateTimePicker6 lbl Label7 llb LinkLabel8 lst ListBox9 lvw ListView10 mT MaskedTextBox11 cdr MonthCalendar12 icn policyicon13 nud NumeircUpDown14 pic PictureBox15 prg ProgressBar16

Use @ to define a string to indicate the character following the compilation as a string For example: string str = @ "C: WindowsExplorer.exe" the system automatically changes the string to "C: \ Windows \ xplorer.exe" during compilation" Equivalent

  The introduction of Linq in C #3.0 makes a profound change in the control of collections. The hero behind this change is the extension method and anonymous type. Here we will talk about anonymous and implicit type variables in C. I,Anonymous

Recently, I used C # To Operate excel. I mainly read the excel template, copied the sheet page of the template, generated multiple sheet pages, filled the corresponding data, and saved it to the excel file, the knowledge points used are as follows. 1

I encountered this problem yesterday afternoon, but the debugging was always successful, but the data was not updated. After searching on the Internet, there are still few such items, probably because the Access database is rarely used, or because

The FindControl method of the System. Web. UI. Control class appears simple enough to use. In fact, the MSDN description of the method is one simple sentence:Searches the current naming container for the specified server control.The key to using

Using System. Runtime. InteropServices; Introduce keyboard event Functions [DllImport ("user32.dll")]Public static extern void keybd_event (byte bVk, byte bScan, int dwFlags, int dwExtraInfo );Parameters: BVk: defines a virtual key code. The key

Private Point mouse_offset;Private void Control_MouseDown (object sender, System. Windows. Forms. MouseEventArgs e){Mouse_offset = new Point (-e. X,-e. Y );}Private void Control_MouseMove (object sender, System. Windows. Forms. MouseEventArgs e){If (