ASP. NET learning notes (III)-Empty data type, strong DataSet

Summer Study: 1. Empty data type: int? Num1 = null; // indicates whether num1 is an empty int type int num2 = num1.value; // num2 = (int) num1;/if (num1.HasValue) returns the string value. format ("Name: {0}, age: {1}", person. name, person. age); 2. use strong DataSet (1) to create a data table. A primary key must be designed. (2) Add a new item under the project you have created.> DATA> DataSet. (3) drag the created table to DataSet to form a DataSet such as T_UsersTableAdapter, that is, the table name + TableAdapter (4) And then directly use T_UsersTableAdapter adapter = New T_UsersTableAdapter (); t_UsersDataTable datatable = T_UsersDataTable (); T_UsersRow row = T_UsersRow (); try encapsulation. dataSet1.T _ UsersDataTable data = adapter. getData (); // do not use adapter. fill () is used only when the file has been obtained locally. It only changes the local data, that is, it has a datatable and then fills it with Fill for (int I = 0; I <data. count; I ++) {try encapsulation. dataSet1.T _ UsersRow userRow = data [I]; MessageBox. show (userRow. userName);} 3. dataSet () can add a custom query statement (1) in the DataSet () designer, add a data table, then fill in the corresponding query statement (2), and then create a function, give him a name by yourself, and directly adapter in the code. use this function (parameter). (3) you can write your own SQL statement in DataTable. 4. stopwatch sw = new Stopwatch (); sw. start (); for (int I = 0; I <100000000; I ++) {}; sw. stop (); MessageBox. show (sw. elapsed. toString (); 5. topic usage (three setting methods) 1. (1) Right-click the website and choose add topic> external File> skinfile to add (2) the specific skin format is to add Font (Font) to the properties of a control ), forecolor (foreground color), bordercolor (border color) (3), and then copy it in the background...Such as the button style code, to the skinfile file, 2. (1) or go to the config file to find
 
  
Tag to add the property theme = "blue", that is:
  
   
In this way, the global style is changed to the blue topic style. Generally, if you do not use the global style (5), you can click in the blank area of the page and select the blue topic in the theme of the property, the premise is that you have added the theme style in app_themes (6). If you do not want to use the global theme, you can change it to fause (8) in the Enabletheme attribute of the control) modify the theme separately based on SkinId = "blue", provided that the global theme is set to true. dynamic topic // separate topic settings. When you click it, the color changes. protected void Page_PreInit (object sender, EventArgs e) {this. theme = "blue ";}