Adding Columns to a DataTable
A DataTable contains a collection of DataColumn objects referenced by the Columns property of the table. This collection of columns, along with any constraints, defines the schema, or structure, of the table.
You create DataColumn objects within a table by using the DataColumn constructor, or by calling the Add method of the Columns property of the table, which is a DataColumnCollection. The Add method accepts optional ColumnName, DataType, and Expression arguments and creates a new DataColumn as a member of the collection. It also accepts an existing DataColumn object and adds it to the collection, and returns a reference to the added DataColumn if requested. Because DataTable objects are not specific to any data source, .NET Framework types are used when specifying the data type of a DataColumn.
The following example adds four columns to a DataTable.
In the example, notice that the properties for the CustID column are set to not allow DBNull values and to constrain values to be unique. However, if you define the CustID column as the primary key column of the table, the AllowDBNull property will automatically be set to false and the Unique property will automatically be set to true. For more information, see Defining Primary Keys.
If a column name is not supplied for a column, the column is given an incremental default name of ColumnN, starting with "Column1", when it is added to the DataColumnCollection. We recommend that you avoid the naming convention of "ColumnN" when you supply a column name, because the name you supply may conflict with an existing default column name in the DataColumnCollection. If the supplied name already exists, an exception is thrown.
If you are using XElement as the DataType of a DataColumn in the DataTable, XML serialization will not work when you read in data. For example, if you write out a XmlDocument by using the method, upon serialization to XML there is an additional parent node in the XElement. To work around this problem, use the SqlXml type instead of XElement. and work correctly with SqlXml.
C# DataTable ExamplesStore data in memory with a DataTable. Add rows, call Compute and Merge, and set PrimaryKey.
DataTable. This class stores rows and columns of data. In C# we can address parts of the DataTable with DataRow and DataColumn. And a DataSet can contain multiple tables.
Step 1 We call GetTable, which generates a table. The returned object could be persisted to disk, displayed, or stored in memory.
Step 2 We create a new DataTable reference. Then we add 4 columns—these include a type, specified with typeof.
Step 3 We add the actual data as rows. The 4 arguments to each Add() call match up with the 4 columns already added.
Step 4 We print a cell value from the first row (row 0) and the Dosage column (which is an int).
C# program that uses DataTable
Generic method Field is a generic method. So we must specify its parametric type (here, int) to indicate its behavior.
Rows Often we must access the rows of a DataTable. The Rows property, which can be looped over, is ideal here.
C# program that uses Rows, Field
Form This code is a Form and can be placed in a Windows Forms application with a DataGridView. It creates a DataTable.
Arrays The 2 arrays are initialized in the class and constructor. They contain column information.
Add We add the column names to our DataTable with Columns.Add. These are the column headers.
Tip DataTable requires objects to assign to the cells. Objects can hold any type of data.
C# program that uses DataGridView
Tip We can add Columns and Rows to the DataTable instance inside (but not outside) the using block.
Tip 2 In this example, the Dispose method is invoked. After the using statement, Dispose() on DataTable is called.
Dispose When Dispose is called, native resources are released. This may help resource usage problems.
C# program that uses using statement
And We call Compute() with a SUM of the column name (like Variety1). The filter argument can be specified as string.Empty.
Result The Total row has the columns summed correctly. We do not need to sum the values with a for-loop.
C# program that uses Compute, SUM expression
Here We create 2 DataTables with names PictureStyle and PictureSize. Each table has a column of IDs, and these IDs match in each table.
PrimaryKey We assign the PrimaryKey to a column (or array of columns). Here we use the ID column, so we can join on the IDs.
Merge We invoke Merge() to join the 2 tables based on their PrimaryKeys. One or more columns can be used.
Result The "PictureStyle" DataTable is updated to include the row fields from the "PictureSize" data table—each row now has 3 cells.
C# program that uses Merge to join DataTables
DataTable Compare Rows
Convert List, DataTable
A summary. DataTable is a powerful, convenient class. We added columns. We added rows. DataTable is faster, in Windows Forms, than manually adding rows. It reduces complexity.
© sam allen. see site info on the changelog
Sum the values in a data set.
Fairly simply, this plug-in will take the data from an API result set and sum it, returning the summed value. The data can come from any data source, including column data, cells or rows.
Note that it will attempt to 'deformat' any string based data that is passed into it - i.e. it will strip any non-numeric characters in order to make a best effort attempt to sum all data types. This can be useful when working with formatting numbers such as currency. However the trade-off is that no error is thrown if non-numeric data is passed in. You should be aware of this in case unexpected values are returned - likely the input data is not what is expected.
This plug-in is available on the DataTables CDN:
Note that if you are using multiple plug-ins, it is beneficial in terms of performance to combine the plug-ins into a single file and host it on your own server, rather than making multiple requests to the DataTables CDN.
If you have any ideas for how this plug-in can be improved, or spot anything that is in error, it is available on GitHub and pull requests are very welcome!
C# program that uses DataColumn
A summary. We looked at the DataColumn class. This type acts as a template for the in-memory relational database abstraction specified by the DataTable type.
© sam allen. see site info on the changelog
Add datatable columns
New rows can be added to a DataTable using the API method. Simply call the API function with the data for the new row (be it an array or object). Multiple rows can be added using the method (note the plural). Data can likewise be updated with the and methods.
Note that in order to see the new row in the table you must call the method, which is easily done through the chaining that the DataTables API employs.
This example shows a single row being added each time the button below is clicked upon.
The Editor extension adds full table editing controls to a DataTable, including creating, editing and deleting rows.
|Column 1||Column 2||Column 3||Column 4||Column 5|
- Server-side script
The HTML shown below is the raw HTML table element, before it has been enhanced by DataTables:
This example uses a little bit of additional CSS beyond what is loaded from the library files (below), in order to correctly display the table. The additional CSS used is shown below:
The following CSS library files are loaded for use in this example to provide the styling of the table:
This table loads data by Ajax. The latest data that has been loaded is shown below. This data will update automatically as any additional data is loaded.
Other examplesSours: https://datatables.net/examples/api/add_row.html
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