C# 从 SQLdatabase 检索 varbinary 数据字段
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时间：2020-08-06 08:09:58 来源:igfitidea点击:
retrieve varbinary datafield from SQLdatabase
提问by Ahmad Farid
i am storing files in database and this is the code i am using and it works in adding the data, but now i want to retrieve it back. how can i do that?
我将文件存储在数据库中，这是我正在使用的代码，它用于添加数据，但现在我想取回它。我怎样才能做到这一点？
string filename = FileUploader.PostedFile.FileName;
string filecontent = FileUploader.PostedFile.ContentType;
int filesize = FileUploader.PostedFile.ContentLength;
string filepath = System.IO.Path.GetFileName(filename);
FileUploader.PostedFile.SaveAs("c:\try\" + filepath);
byte[] fileData = new byte[FileUploader.PostedFile.ContentLength];
FileUploader.PostedFile.InputStream.Read(fileData, 0, fileData.Length);
string originalName = Path.GetFileName(FileUploader.PostedFile.FileName);
con.ConnectionString = System.Web.Configuration.WebConfigurationManager.ConnectionStrings["FAQ"].ToString();
con.Open();
using (SqlCommand cmd = new SqlCommand("INSERT INTO Files(FileData) VALUES (@binaryValue)", con))
{
// Replace 8000, below, with the correct size of the field
cmd.Parameters.Add("@binaryValue", SqlDbType.VarBinary, fileData.Length).Value = fileData;
cmd.ExecuteNonQuery();
con.Close();
}
采纳答案by Eric
You can use a SqlDataReaderto obtain the value, and BinaryWriterto create the file, like so:
您可以使用 aSqlDataReader来获取值，并BinaryWriter创建文件，如下所示：
//Database connection code...
cmd.CommandText = "SELECT FileData FROM Files WHERE ID = @ID";
cmd.Parameters.Add("@ID", SqlDbType.Int).Value = 1234;
SqlDataReader sqlRead = cmd.ExecuteReader();
string fileName = "file.txt";
string fileDir = "C:\Test\";
string fileUrl = "/";
if (sqlRead.HasRows)
{
while(sqlRead.Read())
{
byte[] fileData = (byte[]) sqlRead[0].Value;
BinaryWriter fileCreate =
new BinaryWriter(File.Open(fileDir + fileName, FileMode.Create));
fileCreate.Write(fileData);
fileCreate.Close();
HttpResponse.Redirect(fileUrl + fileName);
}
}
sqlRead.Close();
