从数据库取图片并展示到页面

Posted 2020-10-06 唐家湾

图片以varchar(max)数据格式存储于数据库，每张照片对应一个检测流水号，需要将其取出展示到页面。

一、BLL

publict byte[] GetPhotoData(string jclsh)
{
    byte[] photoData=new byte[4000];
    try
    {
        string sqlStr="select fimage from imagetable where jclsh=\‘"+jclsh+"\‘";
        DataTable dt=new YTH_CHECKPHOTO_DAL().GetDataTable(sqlStr);
        photoData=Convert.FromBase64String(dt.Rows[0]["fimage"].ToString().Replace(" ", "+"));//从Base64String格式转换为byte[]时，需要注意
    }
    catch(Exception ex)
    {
        
    }
    return photoData;
}

二、DAL
1、取得表信息

public override DataTable GetDataTable(string sqlStr)
{
DataTable dt = null;
try
{
//查询DataTable
dt = DbHelper.ExecuteGetDataTable(CommandType.Text, sqlStr);
}
catch (Exception ex)
{
Logger.Error(string.Format(@"执行查询异常，SQL:{0} 异常信息为：{1}", sqlStr, ex.Message));
}
finally
{
CloseConnet();
}
return dt;
}

2、DbHelper执行查询

public static DataTable ExecuteGetDataTable(CommandType commandType, string commandText, params SqlParameter[] commandParameters)
{
    //创建一个SqlCommand对象
    SqlCommand command = new SqlCommand();
    //创建一个DataTable对象
    DataTable table = new DataTable();
    //创建一个SqlConnection对象
    try
    {
        using (SqlConnection sqlConnection = new SqlConnection(connectionString))
        {
            //调用PrepareCommand方法，对SqlCommand对象设置参数
            PrepareCommand(command, sqlConnection, null, commandType, commandText, commandParameters);
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            adapter.Fill(table);
            sqlConnection.Close();
        }
    }
    catch (Exception ex)
    {
        throw ex;
        Logger.Error(ex.Message);
        
    }
    return table;
}

3、DbHelper准备命令 

private static void PrepareCommand(SqlCommand sqlCommand, SqlConnection sqlConnection, SqlTransaction sqlTransaction, CommandType commandType, string commandText, SqlParameter[] commandParameters)
{
    try
    {
        if (sqlConnection.State != ConnectionState.Open)
        {
            sqlConnection.Open();
        }
        sqlCommand.Connection = sqlConnection;
        sqlCommand.CommandText = commandText;
        if (sqlTransaction != null)
        {
            sqlCommand.Transaction = sqlTransaction;

        }
        sqlCommand.CommandType = commandType;
        if (commandParameters != null)
        {
            sqlCommand.Parameters.AddRange(commandParameters);
        }
    }
    catch (Exception ex)
    {
        Logger.Error(ex.Message);
    }
}