[英]Verify existence in database? (MySql & ASP.NET)
尝试将新元素添加到同一数据库时,如何验证数据库中是否已存在某个元素?
我知道它可能需要一些sql代码,但我做不到我想做的事:
这是按钮的完整代码:
protected void Button1_Click(object sender, EventArgs e)
{
if (FileUpload1.PostedFile != null)
{
string FileName = Path.GetFileName(FileUpload1.PostedFile.FileName);
//saves files in the disk
FileUpload1.SaveAs(Server.MapPath("images/" + FileName));
//add an entry to the database
String strConnString = ConfigurationManager.ConnectionStrings["WebAppConnString"].ConnectionString;
MySqlConnection con = new MySqlConnection(strConnString);
string strQuery = "insert into testingdb.country (Relation, FileName, FilePath) values (@Relation, @FileName, @FilePath)";
MySqlCommand cmd = new MySqlCommand(strQuery);
cmd.Connection = con;
cmd.Parameters.AddWithValue("@Relation", TextBox1.Text);
cmd.Parameters.AddWithValue("@FileName", FileName);
cmd.Parameters.AddWithValue("@FilePath", "images/" + FileName);
cmd.CommandType = CommandType.Text;
try
{
if (File.Exists(Server.MapPath("images/" + FileName)))
{
Response.Write("El Objeto ya existe en la base de datos.");
}
else
{
con.Open();
cmd.ExecuteNonQuery();
}
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
finally
{
con.Close();
con.Dispose();
Response.Redirect(Request.Url.AbsoluteUri);
}
}
}
如何做呢? 我有点使用ASP.NET和MySql连接/命令。
我已经找到了答案,我所要做的就是在MapPath()方法之外编写FileName,如下所示:
if (File.Exists(Server.MapPath("images/") + FileName))
{
//mycode & Blah, Blah, Blah.
}
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