ADO.NET

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ExecuteReader - ExecuteNonQuery - ExecuteScaler - ExecuteQuery
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Execute Reader..
1.Returns a datareader with data.
2.It is done by command object.
3.It is readonly.
4.It executes only select command.
5. This is known as a forward-only retrieval of records.It uses your sql statement to read through the table from the first to the last.


Execute NonQuery..
1.It will not return any data.
2.It is used with insert and update.
3.It returns only the number of rows affected.

Execute Scaler..
1.It returns only one value.
2.That value will the first column first row value.
used with aggregate functions like SUM() COUNT() etc

Execute Query..
1.Its for command objects.
2.It returns the value given by database through select statement.

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Convert a DataReader to DataTable in ASP.NET
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SqlConnection conn = null;

try

{

string connString = ConfigurationManager.ConnectionStrings["NorthwindConn"].ConnectionString;

conn = new SqlConnection(connString);

string query = "SELECT * FROM Customers";

SqlCommand cmd = new SqlCommand(query, conn);

conn.Open();

SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);

DataTable dt = new DataTable();

dt.Load(dr);

GridView1.DataSource = dt;

GridView1.DataBind();

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Convert a DataReader to DataTable in ASP.NET (using ADO.NET 1.1)

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string connString = ConfigurationManager.ConnectionStrings["NorthwindConn"].ConnectionString;

conn = new SqlConnection(connString);

string query = "SELECT * FROM Customers";

SqlCommand cmd = new SqlCommand(query, conn);

conn.Open();

SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);

DataTable dtSchema = dr.GetSchemaTable();

DataTable dt = new DataTable();

// You can also use an ArrayList instead of List<>

List listCols = new List();

if (dtSchema != null)

{

foreach (DataRow drow in dtSchema.Rows)

{

string columnName = System.Convert.ToString(drow["ColumnName"]);

DataColumn column = new DataColumn(columnName, (Type)(drow["DataType"]));

column.Unique = (bool)drow["IsUnique"];

column.AllowDBNull = (bool)drow["AllowDBNull"];

column.AutoIncrement = (bool)drow["IsAutoIncrement"];

listCols.Add(column);

dt.Columns.Add(column);

}

}

// Read rows from DataReader and populate the DataTable

while (dr.Read())

{

DataRow dataRow = dt.NewRow();

for (int i = 0; i <>

{

dataRow[((DataColumn)listCols[i])] = dr[i];

}

dt.Rows.Add(dataRow);

}

GridView2.DataSource = dt;

GridView2.DataBind();