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I am trying to insert data from ASP.NET into SQL Server and retrieve it from SQL Server back to ASP.NET.

The insert part is done, but I am having problems to retrieve data. I am using this code, but is throwing an error:

SqlConnection con = new SqlConnection(myconnstrng);
con.Open();

SqlCommand cmd = new SqlCommand("selection", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@id", parameter);

SqlDataAdapter da = new SqlDataAdapter(cmd);

DataSet dsa = new DataSet();
da.Fill(dsa);

if (dsa.Tables[0].Rows.Count > 0)
{
    MemoryStream ms = new MemoryStream((byte[])dsa.Tables[0].Rows[0]["Data"]);
    string strBase64 = Convert.ToBase64String(ms);
    ImageButton2.ImageUrl = "data:Image/png;base64," + strBase64;
}

and the error I got is :

Cannot convert from 'System.IO.MemoryStream' to 'byte[]'

I am new to programming, and if someone could help me about this problem.

Thanks to everyone !

marc_s
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leonard krasniqi
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1 Answers1

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The particular line you are stuck on, you don't need a MemoryStream at all. You can pass the value from the DataTable straight to ToBase64String.

But you can save yourself some bother with these tips:

  1. ALWAYS dispose the connection, command and adapter/reader correctly, by putting them in using blocks`

  2. For a single result, you can skip the table and adapter, and just use (byte[]) cmd.ExecuteScalar().

  3. If you have more than one row which you need to process (as opposed to just displaying in a grid view), you may find it again easier to skip the DataTable and grab data out via this:

using(var reader = cmd.ExecuteReader())
{
    while(reader.Read())
        DoSomethingWithResult(reader.IsDBNull(0) ? null : reader.GetBytes(0));
}

Generally, DoSomethingWithResult should not be very heavy processing, or you will block the SQL server. If so, store in memory and process it afterwards.

Charlieface
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