Object reference not set to an instance of an object

[namrataa]

Hi,
I am working in WPF using C#, SQL server2005, VS2008.
I am trying to download file using HttpContext. But I am getting the error that
"Object reference not set to an instance of an object". Just check the code. When I debug HttpContext is set to null.


CODE:
private void downloadfile()
{

string connectionstring = @"Data Source=01HW107887\SQLEXPRESS;AttachDbFilename=D:\m ainproject\Database\prjectDatabase.mdf;Integrated Security=True"; //ConfigurationManager.ConnectionStrings["prjectDatabaseConnectionString"].ToString();
SqlConnection con = new SqlConnection(connectionstring);
SqlCommand mycommand = new SqlCommand();
mycommand.Connection = con;
con.Open();


string SqlSelect = "select * from Audi where Song_name='" + txtsname.Text + "'";

DataSet ds = new DataSet();
SqlDataAdapter da = new SqlDataAdapter(SqlSelect, con);
da.Fill(ds, "Audi");

string Filename;
if (ds != null)
{
string FileType = ds.Tables["Audi"].Rows[0]["ContentType"].ToString();
byte[] FileContent = (byte[])ds.Tables["Audi"].Rows[0]["song"];
Filename = ds.Tables["Audi"].Rows[0]["Song_name"].ToString();
HttpContext context = HttpContext.Current;
context.Response.Clear();
context.Response.AddHeader("Content-Disposition", "attachment; filename=" + Filename + "." + FileType);
context.Response.AddHeader("Content-Length", FileContent.Length.ToString());
context.Response.ContentType = FileType;
context.Response.OutputStream.Write(FileContent, 0, FileContent.Length);
context.Response.End();

}

con.Close();
}


I don't know the reason for that.

[Ponkarthikeyan]

Hi,
I am working in WPF using C#, SQL server2005, VS2008.
I am trying to download file using HttpContext. But I am getting the error that
"Object reference not set to an instance of an object". Just check the code. When I debug HttpContext is set to null.


CODE:
private void downloadfile()
{

string connectionstring = @"Data Source=01HW107887\SQLEXPRESS;AttachDbFilename=D:\m ainproject\Database\prjectDatabase.mdf;Integrated Security=True"; //ConfigurationManager.ConnectionStrings["prjectDatabaseConnectionString"].ToString();
SqlConnection con = new SqlConnection(connectionstring);
SqlCommand mycommand = new SqlCommand();
mycommand.Connection = con;
con.Open();


string SqlSelect = "select * from Audi where Song_name='" + txtsname.Text + "'";

DataSet ds = new DataSet();
SqlDataAdapter da = new SqlDataAdapter(SqlSelect, con);
da.Fill(ds, "Audi");

string Filename;
if (ds != null)
{
string FileType = ds.Tables["Audi"].Rows[0]["ContentType"].ToString();
byte[] FileContent = (byte[])ds.Tables["Audi"].Rows[0]["song"];
Filename = ds.Tables["Audi"].Rows[0]["Song_name"].ToString();
HttpContext context = HttpContext.Current;
context.Response.Clear();
context.Response.AddHeader("Content-Disposition", "attachment; filename=" + Filename + "." + FileType);
context.Response.AddHeader("Content-Length", FileContent.Length.ToString());
context.Response.ContentType = FileType;
context.Response.OutputStream.Write(FileContent, 0, FileContent.Length);
context.Response.End();

}

con.Close();
}


I don't know the reason for that.

Hi,
This is a common error. If any object is used before initialization then this error will occur. So ensure that every object u r using is initillized before using it. For this find which line error is occured and verify the object at this line is initilized beforehand.

[saran23]

Hi,
I am working in WPF using C#, SQL server2005, VS2008.
I am trying to download file using HttpContext. But I am getting the error that
"Object reference not set to an instance of an object". Just check the code. When I debug HttpContext is set to null.


CODE:
private void downloadfile()
{

string connectionstring = @"Data Source=01HW107887\SQLEXPRESS;AttachDbFilename=D:\m ainproject\Database\prjectDatabase.mdf;Integrated Security=True"; //ConfigurationManager.ConnectionStrings["prjectDatabaseConnectionString"].ToString();
SqlConnection con = new SqlConnection(connectionstring);
SqlCommand mycommand = new SqlCommand();
mycommand.Connection = con;
con.Open();


string SqlSelect = "select * from Audi where Song_name='" + txtsname.Text + "'";

DataSet ds = new DataSet();
SqlDataAdapter da = new SqlDataAdapter(SqlSelect, con);
da.Fill(ds, "Audi");

string Filename;
if (ds != null)
{
string FileType = ds.Tables["Audi"].Rows[0]["ContentType"].ToString();
byte[] FileContent = (byte[])ds.Tables["Audi"].Rows[0]["song"];
Filename = ds.Tables["Audi"].Rows[0]["Song_name"].ToString();
HttpContext context = HttpContext.Current;
context.Response.Clear();
context.Response.AddHeader("Content-Disposition", "attachment; filename=" + Filename + "." + FileType);
context.Response.AddHeader("Content-Length", FileContent.Length.ToString());
context.Response.ContentType = FileType;
context.Response.OutputStream.Write(FileContent, 0, FileContent.Length);
context.Response.End();

}

con.Close();
}


I don't know the reason for that.

The problem is in this line

SqlDataAdapter da = new SqlDataAdapter(SqlSelect, con);

Ur just giving a string as parameter, u hav to pass the command object as parameter, and the string must be used for the command object not here.

it must be

SqlCommand = new SqlCommand(urstring,connection);
SqlDataAdapter da = new SqlDataAdapter(command);

Try it and let me know if it works or not.

Thanks
Saravanan

[namrataa]

The problem is in this line

SqlDataAdapter da = new SqlDataAdapter(SqlSelect, con);

Ur just giving a string as parameter, u hav to pass the command object as parameter, and the string must be used for the command object not here.

it must be

SqlCommand = new SqlCommand(urstring,connection);
SqlDataAdapter da = new SqlDataAdapter(command);

Try it and let me know if it works or not.

Thanks
Saravanan

hi,
I tried it but again it gives me the same error. Does WCF allows HttpContext. It is actually giving error on that line.
HttpContext context=HttpContext.Current

I am stuck over here. Please find any solution