I can't add data from .NET to Access 2010

Button.Click event :

OleDbConnection db_conn;
    db_conn = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\veri.accdb;Persist Security Info=False");
    try
    {
        db_conn.Open();
        OleDbCommand db_command = new OleDbCommand("Insert INTO data(Name,Mail) Values( '" + TextBox1.Text + "','" + TextBox2.Text + "')", db_conn);
        db_command.ExecuteNonQuery();
        db_conn.Close();
        Label5.Text = "Succesfully!";
    }catch{
        Response.Write("There is something wrong!");
    }

The Result is : CATCH : There is something wrong!
My IDE is Visual Studio 2012
My Access version is 2010
My database name is veri.accdb

Solution

Try to change the connection string to

db_conn = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;
                                Data Source=C:\veri.accdb;Persist Security Info=False");

The simple @ in front of the string is required when you have a special character like the backslash. (or use two backslashes like C:\\veri.accdb)

Said that you have another problem. The root of the C: drive is not a good place to position your database because it requires special permissions and usually is a readonly.

Finally the string concatenation is a very bad practice and should be changed to a parameterized query

string cmdText = "Insert INTO data(Name,Mail) Values(?,?)";
using(OleDbConnection db_conn = new OleDbConnection(@"......."))
using(OleDbCommand db_command = new OleDbCommand(cmdText, db_conn)) 
{
    try
    {
        db_conn.Open();
        db_command.Parameters.AddWithValue("@p1",TextBox1.Text);
        db_command.Parameters.AddWithValue("@p2",TextBox2.Text);
        db_command.ExecuteNonQuery();
        Label5.Text = "Succesfully!";
    }
    catch(Exception ex)
    {
        // It is preferable to not catch the exception if you don't do anything, 
        // but if you catch then, at least, report what is wrong
        Response.Write("There is something wrong!" + ex.Message);
    }
 }