Data | A database can treat a DataSet as an in-memory cache of data retrieved from a database. A DataSet consists of a collection of tables, relationships, and constraints.
Private System.Data.SqlClient.SqlDataAdapter SqlDataAdapter1;
Private System.Data.SqlClient.SqlConnection SqlConnection1;
Private System.Data.DataSet dataset=new
Let's talk about DataSet here, this is a powerful thing, we have a preliminary understanding of it in the last section, here we want to talk about it if used to manipulate the data. is also very simple, but powerful, to speak the whole, is unlikely, because the dataset and the DataGrid control account for more than 50% of the. Net help, and this total has 23M ...Here we set up a Test.mdb database, as a test
The core of the ADO. NET Component-Based Development database application, which provides the class required to connect to the data storage and retrieve, operate, and update data. ADO. NET has many components that are implemented in the System. Data namespace. ADO is the abbreviation of ActiveX Data Objects. It is the predecessor of ADO. NET .. NETFramework is the main data access technology of Microsoft. One design goal of ADO. NET is to be closely related to ADO as much as possible, so that de
Use datareader or dataset?
We often hear people ask this question: "in ASP. NET web applicationsProgramShould I use the datareader class or the dataset class ?" In manyArticleAnd I often see this misunderstanding in the newsgroup posts, that is, the datareader (abbreviation of sqldatareader or oledbdatareader) is better than dataset. Sometimes I see the opposi
Method 1: Create a DataSet object
Dataset DS = new dataset ();
Dataset DS = new dataset ("datasetname ");2. Fill dataset with a dataset
The most common method is to fill the data with d
use of DataSet classes in C # The DataSet class is one of the most central members of the Ado.net, and it is the most frequently contacted class for developing database applications based on the. NET Platform programming language. Each dataset has a lot of datatables and relationships. Relationship should also be a kind of table, in particular, this table is on
Enter DataSetAuthor: yuchen
ADO + introduces the concepts of DataSet and DataView. DataSet is similar to a set of records because it can store one or more tables of data and their relationships ). DataView is one of the implementations of these tables, similar to the ADO record set. In the above example, our DataSet only saves one table: Upcoming, which will r
parameters for dataadapter.
IfDatatableYou can useCommandbuilderAutomatic Object generationDataadapterOfDeletecommand,InsertcommandAndUpdatecommand. For more information, see automatically generated commands.
UpdateMethod will resolve the changes back to the data source, but since the last fillingDatasetOther clients may have modified the data in the data source. To use the current data to refreshDataset, Please use it againDataadapterFill (Fill) Dataset
Code:
Using system;
Using system. IO;
Using system. Collections. Generic;
Using system. LINQ;
Using system. Data;
Using system. text;
Using system. runtime. serialization. formatters. Binary;
Namespace simpledataset
{
Class Program
{
Static void main (string [] ARGs)
{
Console. Write ("****** fun with datasets *****/N ");
Dataset carsinventoryds = new dataset ("Car inventory ");
Carsinven
definition of information can be understood as follows. If the transaction to be classified is divided into multiple categories, the information of the symbol Xi is defined
I (xi) =-log2p (xi) where P (xi) is the probability of selecting this classification
To calculate entropy, We need to calculate the expected values of all possible values of all categories. The following formula can be used to obtain the expected values:
Where N is the number of categories
2. Calculate information entropy
1. First, generate a table for link operations. If the two tables are in the same database, I want to use SQL statements directly. There is no need to obtain the local database before link operations; if the two files are not in the same database (for example, the two files in Excel are equivalent to the two databases), you have to extract the data tables you are interested in from each database first, put it in the local datase to form a local database.
2. The datatable object of C # cannot bel
The last time I made the method of using oledb to connect to the database directly in the rpt file, but it was not very flexible. This time I used SQL statements to directly generate dataset as the report data source (that is, the push mode ), in this way, you can accept the parameter. Of course, I have not studied the function of setting parameters in reports in detail.
I. Table association is not used in SQL statements (simple query statements)
1. Obtain the value of a cell in dataset.
Dim DS new dataset
Text1.text = Ds. Tables (0). Rows (row number) (Field name or column number). tostring ()
2. In the table, I represents rows, and j Represents columns.
Dataset. Tables (0). Rows (I) (j)
Dataset. Tables (0). Rows (I). itemarray (j)
3. indicat
Dataset, datatable and datarow replication method
Dataset objects support ADO. the core object of the net disconnected and distributed data solution, which is widely used. we often need to use the data, such as getting data from a able, copying data from another Abe, or data from datarow. However, only the replication of dataset and datatable supports deep repli
How to accept a dataset from an external program in a DLL written by Delphi! Delphi/Windows SDK/API
Http://www.delphi2007.net/DelphiAPI/html/delphi_20061112220726247.html
A dll written by Delphi, how to accept external
ProgramA dataset sent to him!
For example, I wrote a dataset ADODB. recordset in VB and want to transfer it to DLL. Can the interface type i
In fact, Json is a data format. Data is converted into a format in the background, and then parsed in the foreground using the same method, similar to serialization. Json format is mainly composed of key-value pairs, which can represent multiple data. For example{Name: zhangsan, age: 12, class: 1}Json can also represent a dataset consisting of {} And. For example, we need to query a table from the database and transmit the table to the foreground. How
Finding a lot of information on the Internet has found that very few people use the strongly typed data set provided by net.At present, the study of one months, to do the overall summary.First strongly typed data set, strong in there.Datasets We create DataSet if we create it in code, because we don't have a strongly typed definition of a table of code, we have to know the name of the table and the field to execute it.In contrast, the Dateset strongly
ASP + Original Author: share rain
ADO + introduced a DataSet and DataView concept. The DataSet is similar to the record set collection, because it can save one or more data and the relationship between the table (table ). A dataview is these tables, one of the implementation, similar to ADO recordset. In the example above, we DataSet to keep only a table: Upcomi
Tags: log contain enum no Prime Center object content IDT reprinted from: Http://blog.sina.com.cn/s/blog_6faf711d0100za4x.html get the name of the MDB database feature classThe overall idea is as follows:1. Get all DataSet objects in the workspace (Ienumdataset) through the Datasets property of Iworkspace2. Enumerate Enumdataset, get the DataSet object3. If the dataset
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