C#.Net, ASP.Net Data Grid Frequently Asked Questions

a.deeban · #1 (**permalink**) 12-26-2007, 04:03 AM

Hi All,

Here is the space to discuss about data grid using ASP.Net , C#. Net in Web development and Windows application.

thanks..

A. Deeban.

Sathish Kumar · #2 (**permalink**) 12-26-2007, 04:14 AM

Hi,
How can I programatically set the rowheight of a row in my DataGrid?

a.deeban · #3 (**permalink**) 12-26-2007, 04:15 AM

Hi sathish...

Here is a solution . It uses reflection to access the protected DataGridRows collection so he can set the row height.

public void AutoSizeGrid()

{

// DataGrid should be bound to a DataTable for this part to

// work.

int numRows = ((DataTable)gridTasks.DataSource).Rows.Count;

Graphics g = Graphics.FromHwnd(gridTasks.Handle);

StringFormat sf = new StringFormat(StringFormat.GenericTypographic);

SizeF size;

// Since DataGridRows[] is not exposed directly by the DataGrid

// we use reflection to hack internally to it.. There is actually

// a method get_DataGridRows that returns the collection of rows

// that is what we are doing here, and casting it to a System.Array

MethodInfo mi = gridTasks.GetType().GetMethod("get_DataGridRows",

BindingFlags.FlattenHierarchy | BindingFlags.IgnoreCase | BindingFlags.Instance

| BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static);

System.Array dgra = (System.Array)mi.Invoke(gridTasks,null);

// Convert this to an ArrayList, little bit easier to deal with

// that way, plus we can strip out the newrow row.

ArrayList DataGridRows = new ArrayList();

foreach (object dgrr in dgra)

{

if (dgrr.ToString().EndsWith("DataGridRelationshipRow ")==true)

DataGridRows.Add(dgrr);

}

// Now loop through all the rows in the grid

for (int i = 0; i < numRows; ++i)

{

// Here we are telling it that the column width is set to

// 400.. so size will contain the Height it needs to be.

size = g.MeasureString(gridTasks[i,1].ToString(),gridTasks.Font,400,sf);

int h = Convert.ToInt32(size.Height);

// Little extra cellpadding space

h = h + 8;

// Now we pick that row out of the DataGridRows[] Array

// that we have and set it's Height property to what we

// think it should be.

PropertyInfo pi = DataGridRows[i].GetType().GetProperty("Height");

pi.SetValue(DataGridRows[i],h,null);

// I have read here that after you set the Height in this manner that you should

// Call the DataGrid Invalidate() method, but I haven't seen any prob with not calling it..

}

g.Dispose();

}

Thannx...

KiruthikaSambandam · #4 (**permalink**) 12-26-2007, 05:18 AM

Hi,
What’s the difference between the System.Web.UI.WebControls.DataGrid and and System.Windows.Forms.DataGrid?

ThankQ
Kirthika

SaravananJ · #5 (**permalink**) 12-26-2007, 06:26 AM

Hi Kirthika,

The first one System.Web.UI.WebControls.DataGrid is the DataGrid control used in developing web application and the second one System.Windows.Forms.DataGrid is meant for Windows application programming.

Note: All the controls which comes under System.Web namespace is meant for developing web application and the controls which comes under System.Windows namespace is meant for Windows application development

Mramesh · #6 (**permalink**) 12-26-2007, 10:16 PM

Hi all,

Can Anybody tell me how to remove the duplicate rows in a dataset please. If possible give me sample code.

Thanx in Advance...

M. Ramesh kumar

Sundaram · #7 (**permalink**) 12-26-2007, 10:28 PM

Hi Ramesh,

This method will remove the duplicate rows from a datatable, based on a column. Pass to the method the datatable and the column to be checked for duplicate values.

Call the method like this :

Code:

RemoveDuplicateRows(dT,"ID");

This is the implementation.

Code:

public void RemoveDuplicateRows(DataTable dTable,string colName)
{
        Hashtable hTable = new Hashtable();
        ArrayList duplicateList = new ArrayList();

        foreach(DataRow drow in dTable.Rows)
        {
                try
                {
                            hTable.Add(drow[colName],string.Empty);
                }
                catch
                {
                        duplicateList.Add(drow); 
                }
         }

          foreach(DataRow dRow in duplicateList)
                   dTable.Rows.Remove(dRow);
}

Cheers !
Sundaram

Sathish Kumar · #8 (**permalink**) 12-26-2007, 10:38 PM

hi all,

copy past this code and make change with ur app path etc...

Code:

 cmd.CommandText = "delete from emp where id not in (select min(id) from emp group by name,address)"
       cmd.ExecuteNonQuery()
       da.SelectCommand = cmd
       da.Fill(ds, "emp")
       DataGrid1.DataSource = ds.Tables("emp")
       DataGrid1.SetDataBinding(ds, "emp")
       DataGrid1.Refresh()

Regards,

SathisKumar R

Sathish Kumar · #9 (**permalink**) 12-27-2007, 11:55 PM

Hi guys,
I must add custom ColumnStyles to the designer so I can use them in a DataGrid at design time.Can anybody tell me how to do this?

a.deeban · #10 (**permalink**) 12-27-2007, 11:58 PM

Hi sathish...

To use custom ColumnStyles in the designer, you need to do three things.

1) Derive a CustomColumnStyle to implement the functionality you want.

2) Derive a DataGridTableStyle class and add a new GridColumnStyles property that uses this derived CollectionEditor. This GridColumnStyle hides the base class member.

3) Derive a DataGrid and add a new TableStyles collection that uses your derived table style.

Both steps 2 and 3 will require you to derive a CollectionEditor and override CreateNewItemTypes to use the derived classes from each step in the designer.

Thnx...

Sathish Kumar · #11 (**permalink**) 12-28-2007, 12:02 AM

Hi,
I am losing the settings on a DataGrid set during design-time.Do anybody know why this happens?

a.deeban · #12 (**permalink**) 12-28-2007, 12:04 AM

Hi Sathish...

This is possible if you assign a custom DataGridTableStyle to the DataGrid. The properties in the DataGridTableStyle will then replace certain properties in the DataGrid. Take a look at DataGrid class reference for a list of these properties.

Thnx..

shaalini · #13 (**permalink**) 12-28-2007, 01:37 AM

hi,
How to add a new row in the datagrid when each time add button is clicked

a.deeban · #14 (**permalink**) 01-02-2008, 09:54 PM

Hi..

The important thing to know about your question is that you can't add a row to a datagrid, you must add a row to the datasource for the grid then re-bind the grid.

Usually, the datasource for the grid is some class that has a item count property. From that you can determine the last item index, then add 1, set the EditItemIndex of the grid to that value and re-bind the grid. Now you have a "new row" in the grid that is set up for data entry. Then you just need to modify your logic a bit to do a data insert instead of an update. When you save the row.

Hope this will help you...

a.deeban · #15 (**permalink**) 01-02-2008, 10:06 PM

Hi...

Here is the sample source code...

ASP. Net Source

Code:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs" AutoEventWireup="false" Inherits="TestDGrid.WebForm1" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
	<HEAD>
		<title>WebForm1</title>
		<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
		<meta name="CODE_LANGUAGE" Content="C#">
		<meta name="vs_defaultClientScript" content="JavaScript">
		<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
	</HEAD>
	<body MS_POSITIONING="GridLayout">
		<form id="Form1" method="post" runat="server">
			<asp:DataGrid id="DataGrid1" style="Z-INDEX: 101; LEFT: 112px; POSITION: absolute; TOP: 16px"
				runat="server" AutoGenerateColumns="False">
				<Columns>
					<asp:TemplateColumn HeaderText="Id">
						<ItemTemplate>
							<asp:TextBox id="txtID" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "iEid ") %>'>
							</asp:TextBox>
						</ItemTemplate>
					</asp:TemplateColumn>
					<asp:TemplateColumn HeaderText="Name">
						<ItemTemplate>
							<asp:TextBox id="txtName" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "cEName") %>'>
							</asp:TextBox>
						</ItemTemplate>
					</asp:TemplateColumn>
					<asp:TemplateColumn HeaderText="Salary">
						<ItemTemplate>
							<asp:TextBox id="txtSal" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "dSalary") %>'>
							</asp:TextBox>
						</ItemTemplate>
					</asp:TemplateColumn>
				</Columns>
			</asp:DataGrid>
			<asp:Button id="btAdd" style="Z-INDEX: 102; LEFT: 64px; POSITION: absolute; TOP: 24px" runat="server"
				Text="Add"></asp:Button>
		</form>
	</body>
</HTML>

C# Source:

Code:

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
namespace TestDGrid
{
	/// <summary>
	/// Summary description for WebForm1.
	/// </summary>
	
	public class WebForm1 : System.Web.UI.Page
	{
		protected System.Web.UI.WebControls.DataGrid DataGrid1;
		protected DataTable table = new DataTable();
		protected System.Web.UI.WebControls.Button btAdd;
		SqlConnection con = new SqlConnection(@"Server=Servername;DataBase=database name;uid=sa;pwd=sa;");
	
		private void Page_Load(object sender, System.EventArgs e)
		{
			// Put user code to initialize the page here
			if(!IsPostBack)
			{   fill();
				BindDG();
			}
		}

		public void fill()
		{
			SqlDataAdapter da = new SqlDataAdapter("Select * from emp",con);
			DataSet ds = new DataSet();
			da.Fill(table);
			
		}

		public void BindDG()
		{
			DataGrid1.DataSource=table;
			DataGrid1.DataBind();
		}

		public void Nrow()
		{
			table.Rows.InsertAt(table.NewRow(),0);
			
		}

		#region Web Form Designer generated code
		override protected void OnInit(EventArgs e)
		{
			//
			// CODEGEN: This call is required by the ASP.NET Web Form Designer.
			//
			InitializeComponent();
			base.OnInit(e);
		}
		
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{    
			this.btAdd.Click += new System.EventHandler(this.btAdd_Click);
			this.Load += new System.EventHandler(this.Page_Load);

		}
		#endregion

		private void btAdd_Click(object sender, System.EventArgs e)
		{
		DataGrid1.CurrentPageIndex = 0;
			fill();
			Nrow();
			BindDG();
			
		}
	}
}

I hope this will help you...

a.deeban · #16 (**permalink**) 01-17-2008, 05:18 AM

Hi All...

How do I prevent the datagrid from displaying its append row (the row at the end with an asterisk)?

thnkx...

Sathish Kumar · #17 (**permalink**) 01-17-2008, 05:21 AM

Hi,
The DataGrid class does not have a property that controls whether a new row can be added. But the DataView class does have such a property (along with some others such as AllowEdit and AllowDelete).

a.deeban · #18 (**permalink**) 01-17-2008, 05:22 AM

Hi Sathish...

Thanks for your reply, can you send me the code using dataview...

thnx again...

Sathish Kumar · #19 (**permalink**) 01-17-2008, 05:24 AM

Hi,
Here is the sample code.

Code:

string connString = @"Provider=Microsoft.JET.OLEDB.4.0;data source=C:\northwind.mdb"; 
 
     string sqlString = "SELECT * FROM customers"; 
 

 
     // Connection object 
 
     OleDbConnection connection = new OleDbConnection(connString); 
 

 
     // Create data adapter object 
 
     OleDbDataAdapter dataAdapter = new OleDbDataAdapter(sqlString, connection); 
 

 
     // Create a dataset object and fill with data using data adapter's Fill method 
 
     DataSet dataSet = new DataSet(); 
 
     dataAdapter.Fill(dataSet, "customers"); 
 
                
 
     // Attach dataset's DefaultView to the datagrid control 
 
     dataGrid1.DataSource = dataSet.Tables["customers"]; 
 

 
     //no adding of new rows thru dataview... 
 
     CurrencyManager cm = (CurrencyManager)this.BindingContext[dataGrid1.DataSource, dataGrid1.DataMember];      
 
     ((DataView)cm.List).AllowNew = false;

Sathish Kumar · #20 (**permalink**) 01-17-2008, 05:27 AM

Hi,
If your datagrid contains links, then I would suggest adding Navigate handler such as the one below to disallow the AddNew.

Code:

private void DataGrid1_Navigate(object sender, System.Windows.Forms.NavigateEventArgs ne) 
 
{ 
 
     if(ne.Forward) 
 
     { 
 
          CurrencyManager cm = (CurrencyManager)BindingContext[DataGrid1.DataSource,DataGrid1.DataMember]; 
 
          DataView dv = (DataView) cm.List; 
 
          dv.AllowNew = false; 
 
     } 
 
}

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