how to upload an excel in c# ASP.Net?
protected void btnUpload_Click(object sender, EventArgs e)
{
if (fuUpload.HasFile)
{
string filename = fuUpload.PostedFile.FileName;
string strConn;
strConn = "Provider=Microsoft.Jet.OLEDB.4.0;"
+"Data Source="+ filename +";" +"Extended Properties=Excel
8.0;";
OleDbConnection con = new OleDbConnection(strConn);
con.Open();
OleDbCommand cmd = new OleDbCommand("select *
from [Sheet1$]",con);
OleDbDataAdapter dad = new OleDbDataAdapter();
dad.SelectCommand = cmd;
DataSet ds= new DataSet();
dad.Fill(ds);
DataGrid1.DataSource = ds.Tables[0].DefaultView;
DataGrid1.DataBind();
con.Close();
}
}
What are the various objects in Dataset?
The DataSet class exists in the System.Data namespace. The Classes contained in the DataSet class are:
DataTable
DataColumn
DataRow
Constraint
DataRelation.
ASP .NET Interview Questions, Part 1
1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process. inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension),the ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker process aspnet_wp.exe.
2. What’s the difference between Response.Write() andResponse.Output.Write()? The latter one allows you to write formattedoutput.
3. What methods are fired during the page load? Init() – when the pageis instantiated, Load() – when the page is loaded into server memory,PreRender() – the brief moment before the page is displayed to the user asHTML, Unload() – when page finishes loading.
4. Where does the Web page belong in the .NET Framework class hierarchy?System.Web.UI.Page
5. Where do you store the information about the user’s locale? System.Web.UI.Page.Culture
6. What’s the difference between Codebehind=”MyCode.aspx.cs” andSrc=”MyCode.aspx.cs”? CodeBehind is relevant to Visual Studio.NET only.
7. What’s a bubbled event? When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.
8. Suppose you want a certain ASP.NET function executed on MouseOver overa certain button. Where do you add an event handler? It’s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add(“onMouseOver”,”someClientCode();”)
9. What data type does the RangeValidator control support? Integer,String and Date.
10. Explain the differences between Server-side and Client-side code? Server-side code runs on the server. Client-side code runs in the clients’ browser.
11. What type of code (server or client) is found in a Code-Behind class? Server-side code.
12. Should validation (did the user enter a real date) occur server-side or client-side? Why? Client-side. This reduces an additional request to the server to validate the users input.
13. What does the “EnableViewState” property do? Why would I want it on or off? It enables the viewstate on the page. It allows the page to save the users input on a form.
14. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other? Server.Transfer is used to post a form to another page. Response.Redirect is used to redirect the user to another page or site.
15. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
· A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
· A DataSet is designed to work without any continuing connection to the original data source.
· Data in a DataSet is bulk-loaded, rather than being loaded on demand.
· There’s no concept of cursor types in a DataSet.
· DataSets have no current record pointer You can use For Each loops to move through the data.
· You can store many edits in a DataSet, and write them to the original data source in a single operation.
· Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.
16. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines? This is where you can set the specific variables for the Application and Session objects.
17. If I’m developing an application that must accommodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing) what would be the best approach to maintain login-in state for the users? Maintain the login state security through a database.
18. Can you explain what inheritance is and an example of when you might use it? When you want to inherit (use the functionality of) another class. Base Class Employee. A Manager class could be derived from the Employee base class.
asp.net interview questions and answers
How do we do paging in gridview?
Make Allowpaging=true also specify the PageIndex as some value
Namespace and Assembly?
Namespace is a logical design-time naming convenience, whereas an assembly establishes the name scope for types at run time.
Diff b/w dataset.clone and dataset.copy
dataset.clone copies just the structure of dataset (including all the datatables, schemas, relations and constraints.); however it doesn’t copy the data. On the other hand dataset.copy, copies both the dataset structure and the data.
Diff b/w Const and readonly?
A const can not be static, while readonly can be static.
A const need to be declared and initialized at declaration only, while a readonly can be initialized at declaration or by the code in the constructor.
A const’s value is evaluated at design time, while a readonly’s value is evaluated at runtime.
Diversities between static or dynamic assemblies ?
Assemblies can be static or dynamic.
Static assemblies can include .NET Framework types (interfaces and classes), as well as resources for the assembly (bitmaps, JPEG files, resource files, and so on).
Static assemblies are stored on disk in portable executable (PE) files.
You can also use the .NET Framework to create dynamic assemblies, which are run directly from memory and are not saved to disk before execution.You can save dynamic assemblies to disk after they have executed.
How can you show the number of visitors of your app
By havving an application variable and Incrementing it in every session start.
TO Achieve it use the Global.asax file's Application_Start and Session_Start Events.
What is the difference between ADO and ADO.NET?
ADO uses Recordsets and cursors to access and modify data. Because of its inherent design, Recordset can impact performance on the server side by tying up valuable resources. In addition, COM marshalling - an expensive data conversion process - is needed to transmit a Recordset. ADO.NET addresses three important needs that ADO doesn't address: 
1. Providing a comprehensive disconnected data-access model, which is crucial to the Web environment
2. Providing tight integration with XM
3. Providing seamless integration with the .NET Framework (e.g., compatibility with the base class library's type system). From an ADO.NET implementation perspective, the Recordset object in ADO is eliminated in the .NET architecture. In its place, ADO.NET has several dedicated objects led by the DataSet object and including the DataAdapter, and DataReader objects to perform specific tasks. In addition, ADO.NET DataSets operate in disconnected state whereas the ADO RecordSet objects operated in a fully connected state.
In ADO, the in-memory representation of data is the RecordSet. In ADO.NET, it is the dataset. A RecordSet looks like a single table. If a RecordSet is to contain data from multiple database tables, it must use a JOIN query, which assembles the data from the various database tables into a single result table. In contrast, a dataset is a collection of one or more tables. The tables within a dataset are called data tables; specifically, they are DataTable objects. If a dataset contains data from multiple database tables, it will typically contain multiple DataTable objects. That is, each DataTable object typically corresponds to a single database table or view. In this way, a dataset can mimic the structure of the underlying database.
In ADO you scan sequentially through the rows of the RecordSet using the ADO MoveNext method. In ADO.NET, rows are represented as collections, so you can loop through a table as you would through any collection, or access particular rows via ordinal or primary key index. A cursor is a database element that controls record navigation, the ability to update data, and the visibility of changes made to the database by other users. ADO.NET does not have an inherent cursor object, but instead includes data classes that provide the functionality of a traditional cursor. For example, the functionality of a forward-only, read-only cursor is available in the ADO.NET DataReader object.
There is one significant difference between disconnected processing in ADO and ADO.NET. In ADO you communicate with the database by making calls to an OLE DB provider. In ADO.NET you communicate with the database through a data adapter (an OleDbDataAdapter, SqlDataAdapter, OdbcDataAdapter, or OracleDataAdapter object), which makes calls to an OLE DB provider or the APIs provided by the underlying data source.
Asp.net Interview: Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
In ADO, the in-memory representation of data is the recordset. In ADO.NET, it is the dataset. There are important differences between them.
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A recordset looks like a single table. If a recordset is to contain data from multiple database tables, it must use a JOIN query, which assembles the data from the various database tables into a single result table. In contrast, a dataset is a collection of one or more tables. The tables within a dataset are called data tables; specifically, they are DataTable objects. If a dataset contains data from multiple database tables, it will typically contain multiple DataTable objects. That is, each DataTable object typically corresponds to a single database table or view. In this way, a dataset can mimic the structure of the underlying database. A dataset usually also contains relationships. A relationship within a dataset is analogous to a foreign-key relationship in a database —that is, it associates rows of the tables with each other. For example, if a dataset contains a table about investors and another table about each investor’s stock purchases, it could also contain a relationship connecting each row of the investor table with the corresponding rows of the purchase table. Because the dataset can hold multiple, separate tables and maintain information about relationships between them, it can hold much richer data structures than a recordset, including self-relating tables and tables with many-to-many relationships.
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In ADO you scan sequentially through the rows of the recordset using the ADO MoveNext method. In ADO.NET, rows are represented as collections, so you can loop through a table as you would through any collection, or access particular rows via ordinal or primary key index. DataRelation objects maintain information about master and detail records and provide a method that allows you to get records related to the one you are working with. For example, starting from the row of the Investor table for "Nate Sun," you can navigate to the set of rows of the Purchase table describing his purchases. A cursor is a database element that controls record navigation, the ability to update data, and the visibility of changes made to the database by other users. ADO.NET does not have an inherent cursor object, but instead includes data classes that provide the functionality of a traditional cursor. For example, the functionality of a forward-only, read-only cursor is available in the ADO.NET DataReader object. For more information about cursor functionality, see Data Access Technologies.
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Minimized Open Connections: In ADO.NET you open connections only long enough to perform a database operation, such as a Select or Update. You can read rows into a dataset and then work with them without staying connected to the data source. In ADO the recordset can provide disconnected access, but ADO is designed primarily for connected access. There is one significant difference between disconnected processing in ADO and ADO.NET. In ADO you communicate with the database by making calls to an OLE DB provider. In ADO.NET you communicate with the database through a data adapter (an OleDbDataAdapter, SqlDataAdapter, OdbcDataAdapter, or OracleDataAdapter object), which makes calls to an OLE DB provider or the APIs provided by the underlying data source. The important difference is that in ADO.NET the data adapter allows you to control how the changes to the dataset are transmitted to the database — by optimizing for performance, performing data validation checks, or adding any other extra processing. Data adapters, data connections, data commands, and data readers are the components that make up a .NET Framework data provider. Microsoft and third-party providers can make available other .NET Framework data providers that can be integrated into Visual Studio.
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Sharing Data Between Applications. Transmitting an ADO.NET dataset between applications is much easier than transmitting an ADO disconnected recordset. To transmit an ADO disconnected recordset from one component to another, you use COM marshalling. To transmit data in ADO.NET, you use a dataset, which can transmit an XML stream.
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Richer data types.COM marshalling provides a limited set of data types — those defined by the COM standard. Because the transmission of datasets in ADO.NET is based on an XML format, there is no restriction on data types. Thus, the components sharing the dataset can use whatever rich set of data types they would ordinarily use.
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Performance. Transmitting a large ADO recordset or a large ADO.NET dataset can consume network resources; as the amount of data grows, the stress placed on the network also rises. Both ADO and ADO.NET let you minimize which data is transmitted. But ADO.NET offers another performance advantage, in that ADO.NET does not require data-type conversions. ADO, which requires COM marshalling to transmit records sets among components, does require that ADO data types be converted to COM data types.
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Penetrating Firewalls.A firewall can interfere with two components trying to transmit disconnected ADO recordsets. Remember, firewalls are typically configured to allow HTML text to pass, but to prevent system-level requests (such as COM marshalling) from passing.
