This provides a list of ADO.NET FAQs-3 which are of "Difference between" kind

1. 1.Difference between ExecuteNonQuery() and ExecuteScalar() methods in ADO.NET
S.No ExecuteNonQuery() ExecuteScalar()
1 It will work with Action Queries It will work with Non-Action Queries
only that contain aggregate functions.
(Create,Alter,Drop,Insert,Update,
Delete).
2 It returns the count of rows It returns the first row and first column
effected by the Query. value of the query result.
3 Return type is int Return type is object.
4 Return value is optional and can Return value is compulsory and should
be assigned to an integer variable. be assigned to a variable of required
type.
Example-1 for ExecuteNonQuery Method -Insert:
SqlCommand cmd = new SqlCommand("Insert Into SampleTable Values('1','2')",con);
//con is the connection object
con.Open();
cmd.ExecuteNonQuery(); //The SQL Insert Statement gets executed
Example-2 for ExecuteNonQuery Method - Update:
public void UpdateEmployeeEmail()
{
SqlConnection conn = new SqlConnection(connString))
String sqlQuery = "UPDATE Employee SET empemail='umar.ali@xyz.com' WHERE
empid=5;
SqlCommand cmd = new SqlCommand(sqlQuery, conn);
try
{
conn.Open();
cmd.ExecuteNonQuery();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
conn.Close();
}
return count;
}

2. Example-1 for ExecuteScalar Method:
This returns only one value that is first column value of the first row in the executed query
public int getSomeProdId()
{
int count=0;
SqlConnection conn = new SqlConnection(connString))
String sqlQuery = "SELECT COUNT(*) FROM dbo.region";
SqlCommand cmd = new SqlCommand(sqlQuery, conn);
try
{
conn.Open();
//Since return type is System.Object, a typecast is must
count = (Int32)cmd.ExecuteScalar();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
conn.Close();
}
return count;
}
Example-2 for ExecuteScalar Method:
This returns one value only, no recordsets.
cmd.CommandText = "Select Name, DOB, from Emp where ID=1";
Dim strName As string = cmd.ExecuteScalar.ToString
2.Difference between ExecuteNonQuery() and ExecuteReader() methods in ADO.NET
S.No ExecuteNonQuery() ExecuteReader()
1 It will work with Action Queries It will work with Action and Non-
only Action Queries (Select)
(Create,Alter,Drop,Insert,Update,
Delete).
2 It returns the count of rows It returns the collection of rows
effected by the Query. selected by the Query.
3 Return type is int Return type is DataReader.
4 Return value is optional and can Return value is compulsory and should

3. be assigned to an integer variable. be assigned to an another object
DataReader.
Example-1 for ExecuteNonQuery Method -Insert:
SqlCommand cmd = new SqlCommand("Insert Into SampleTable Values('1','2')",con);
//con is the connection object
con.Open();
cmd.ExecuteNonQuery(); //The SQL Insert Statement gets executed
Example-2 for ExecuteNonQuery Method - Update:
public void UpdateEmployeeEmail()
{
SqlConnection conn = new SqlConnection(connString))
String sqlQuery = "UPDATE Employee SET empemail='umar.ali@xyz.com' WHERE
empid=5;
SqlCommand cmd = new SqlCommand(sqlQuery, conn);
try
{
conn.Open();
cmd.ExecuteNonQuery();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
conn.Close();
}
return count;
}
Example for ExecuteReader Method:
Here, ExecuteReader is used to get set of records by specified query, namely, "select * from emp"
SqlConnection con = new SqlConnection(constr); //constructor can be connection of string.
SqlCommand cmd = new SqlCommand ("select * from emp", con);
con.Open();
SqlDataReader dr = cmd. ExecuteReader (CommandBehavior. CloseConnection); //Implicitly
closes the connection because CommandBehavior. CloseConnection was specified.
while(dr.Read())
{
Console.WriteLine (dr.GetString(0));
}
dr.Close();

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