downloading files in .NET urgent

[rajnow]

How can i download files like(.doc,.txt,.pdf,.gif) which are already uploaded to databse in asp.net using c#,plz help me regarding this

[kenobewan]

Welcome to TSDN. Please explain and provide more info. Thanks.

[RoninZA]

Hello rajnow...

I am assuming that you want to download a file that is stored in a table in a database, in, for example, an image column...

The solution is pretty intricate, downloading the file in chunks, but see code below (this uses the SQLHelper class, but you could quite comfortable write code to replace that as well (variables in $-signs need to be provided):

System.Data.SqlClient.SqlConnection cn = null;
int offset = 0;
 
System.Data.SqlClient.SqlParameter[] pointerParams = 
    new System.Data.SqlClient.SqlParameter[2];
 
string selectSql = @"
    SELECT    @pointer = TEXTPTR(" + $fieldName$ + @"),
        @length = DataLength(" + $fieldName$ + @")
    FROM    " + $tableName$ + @"
    WHERE    " + $whereClause$;
 
pointerParams[0] = new System.Data.SqlClient.SqlParameter("@pointer", SqlDbType.Binary, 16);
pointerParams[1] = new System.Data.SqlClient.SqlParameter("@length", SqlDbType.Int, 4);
pointerParams[0].Direction = ParameterDirection.Output;
pointerParams[1].Direction = ParameterDirection.Output;
 
DAL.SqlHelper.ExecuteNonQuery(
    $connectionString$, 
    CommandType.Text, 
    selectSql, 
    pointerParams);
 
cn = new System.Data.SqlClient.SqlConnection($connectionString$);
cn.Open();
 
if (cn.State != ConnectionState.Open)
    return null;
 
System.Data.SqlClient.SqlCommand cmdRead = new System.Data.SqlClient.SqlCommand(
    "READTEXT " + $tableName$ + "." + $fieldName$ + @" @Pointer @Offset @Size HOLDLOCK", cn);
 
System.Data.SqlClient.SqlParameter pointerParam = cmdRead.Parameters.Add("@Pointer", SqlDbType.Binary, 16);
System.Data.SqlClient.SqlParameter offsetParam = cmdRead.Parameters.Add("@Offset", SqlDbType.Int);
System.Data.SqlClient.SqlParameter sizeParam = cmdRead.Parameters.Add("@Size", SqlDbType.Int);
pointerParam.Value = pointerParams[0].Value;
offsetParam.Value = 0;
 
System.Data.IDataReader reader;
 
byte[] buffer = new byte[System.Convert.ToInt32(pointerParams[1].Value)];
do
{
    pointerParam.Value = pointerParams[0].Value;
    if ((offset + $BufferChunkLength$) >= System.Convert.ToInt32(pointerParams[1].Value))
        sizeParam.Value = System.Convert.ToInt32(pointerParams[1].Value) - offset;
    else 
        sizeParam.Value = $BufferChunkLength$;
 
    reader = cmdRead.ExecuteReader(CommandBehavior.SingleResult);
    reader.Read();
    reader.GetBytes(0, 0, buffer, offset, System.Convert.ToInt32(sizeParam.Value));
    reader.Close();
    offset += System.Convert.ToInt32(sizeParam.Value);
    offsetParam.Value = offset;
 
} while (offset < Convert.ToInt32(pointerParams[1].Value));
 
return buffer;