How to insert a c# datetime var into SQL Server

Here is the code:

string ConnectionString= @"Data Source=localhost\SQLEXPRESS; 
Initial Catalog=notepad; Integrated Security=SSPI ";
SqlConnection con = new SqlConnection(ConnectionString); 
con.Open();
string strEvent = TextBoxEvent.Text;
string strDate = Calendar1.TodaysDate.ToShortDateString();
string strInsert = "insert into notepad (time, event) values (strDate, strEvent )";
SqlCommand cmd=new SqlCommand(strInsert, con);
cmd.ExecuteNonQuery();

the time is smalldatetime in SQL Server 2005

When I run this program, an error occurrs like this:

The name "strDate" is not permitted in this context. Valid expressions are constants, constant expressions, and (in some contexts) variables. Column names are not permitted.

but if I replace the strDate with 2010/05/22 like this:

string strInsert = "insert into notepad (time, event) values ("2010/05/22", strEvent )";

t开发者_高级运维he program will run correctly.

I am puzzled with this problem and turn for help to you.

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You should use parametrized queries for inserting data into SQL Server, and you should put your SqlConnection and SqlCommand into using blocks - try something like this:

string ConnectionString= @"Data Source=localhost\SQLEXPRESS; 
Initial Catalog=notepad; Integrated Security=SSPI ";

string sqlStatement = "INSERT INTO dbo.Notepad(time, event) VALUES (@Date, @Event)";

using(SqlConnection con = new SqlConnection(ConnectionString))
using(SqlCommand cmd = new SqlCommand(sqlStatement, con))
{
   cmd.Parameters.Add("@Date", SqlDbType.DateTime).Value = Calendar1.TodaysDate;
   cmd.Parameters.Add("@Event", SqlDbType.VarChar, 100).Value = TextBoxEvent.Text.Trim();

   con.Open();
   cmd.ExecuteNonQuery();
   con.Close();
}

Also, this is mixing your database access code with your UI code (retrieving data from textbox and calendar control) - this is a bad practice - you should separate this into two steps:

1. grab the current values from the UI in your code-behind file
2. pass them to a data layer which handles data access without ever directly touching any UI controls

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All the methods here said are good but I prefer the following one because its has an edge over the other ones

DataAccess DAB = new DataAccess();
ArrayList arrList = new ArrayList();
string SQL = " insert into notepad (time, event) values (?,?) ";
arrList.Add(new DataAccessBlock.DataAccess.Parameter("@time",  DbType.DateTime, 30, ParameterDirection.Input, "", strDate ));    
arrList.Add(new DataAccessBlock.DataAccess.Parameter("@event", DbType.String, 50, ParameterDirection.Input, "", strEvent ));

DAB.ExecuteScalar(SQL, CommandType.Text, arrList);

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This statement below is wrong because you are actually including strDate instead of substituting its value.

string strInsert = "insert into notepad (time, event) values (strDate, strEvent )";

What you need to do is write as follows:

string strInsert = "insert into notepad (time, event) values ("+strDate+"," +strEvent+)";

This will substitute strDate and strEvent with the actual values at runtime.

*This approach however is NOT recommended because it is prone to SQL injection attacks *