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QuestPond’s Interview Questions & Answers on ADO.NET

How can we save all data from dataset?

Dataset has “AcceptChanges” method, which commits all the changes since last time “Acceptchanges” has been executed.

How can we check which rows have changed since dataset was loaded?

For tracking down changes, Dataset has two methods, which comes to rescue “Get Changes “and “Has Changes”.

Get Changes
Returns dataset, which are changed since it, was loaded, or since Accept changes was executed.

Has Changes
Or abandon all changes since the dataset was loaded use “Reject Changes This property indicates that has any changes been made since the dataset was loaded or accept changes method was executed.

How can we add/remove row is in “Data Table” object of “Dataset”?

“Data table” provides “NewRow” method to add new row to “Data Table”. “Data Table” has “DataRowCollection” object that has all rows in a “Data Table” object. Following are the methods provided by “DataRowCollection” object:-

Add
Adds a new row in Data Table

Remove
It removes a “Data Row” object from “Data Table”

Remove At
It removes a “Data Row” object from “Data Table” depending on index position of the “Data Table”.

How can we load multiple tables in a Dataset?

objCommand.CommandText = "Table1"
objDataAdapter.Fill(objDataSet, "Table1")
objCommand.CommandText = "Table2"
objDataAdapter.Fill(objDataSet, "Table2")


Above is a sample code, which shows how to load multiple “Data Table” objects in one “Dataset” object. Sample code shows two tables “Table1” and “Table2” in object ObjDataSet.


lstdata.DataSource = objDataSet.Tables("Table1").DefaultView

In order to refer “Table1” Data Table, use Tables collection of Datasets and the Default view object will give you the necessary output.

How can we add relation between tables in a Dataset?

Dim objRelation As DataRelation
objRelation=New
DataRelation("CustomerAddresses",objDataSet.Tables("Customer").Columns("Custid")
,objDataSet.Tables("Addresses").Columns("Custid_fk"))
objDataSet.Relations.Add(objRelation)


Relations can be added between “Data Table” objects using the “Data Relation” object. Above sample, code is trying to build a relationship between “Customer” and “Addresses” “Data table” using “Customer Addresses” “Data Relation” object.

See the following video on Dataset is a disconnect while datareader is connected: -



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