Boolean fileOk = false;
string path = Server.MapPath("~/images/");
//判断是否已经选取文件
if (FileUpload1.HasFile)
{ //取得文件的扩展名,并转换成小写 string fileExtension = System.IO.Path.GetExtension(FileUpload1.FileName).ToLower(); //限定只能上传jpg和gif图片 string[] allowExtension = { ".jpg", ".gif" }; //对上传的文件的类型进行一个个匹对 int j = 0; for (int i = 0; i < allowExtension.Length; i++) { if (fileExtension == allowExtension[i]) { fileOk = true; return; } else { j++; } } if (j > 0) { Response.Write("<script>alert('文件格式不正确');</script>"); return; }
}
else
{ Response.Write("<script>alert('你还没有选择文件');</script>"); return;
}
//如果扩展名符合条件，则上传
if (fileOk)
{ FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName); Response.Write("<script>alert('上传成功');</script>");
}

Boolean fileOk = false;
string path = Server.MapPath("~/images/");
//判断是否已经选取文件
if (FileUpload1.HasFile)
{ //取得文件MIME内容类型 string type = this.FileUpload1.PostedFile.ContentType.ToLower(); if (type.Contains("image"))    //图片的MIME类型为"image/xxx"，这里只判断是否图片。 { fileOk = true; } else { Response.Write("<script>alert('格式不正确')</script>"); }
}
else
{ Response.Write("<script>alert('你还没有选择文件');</script>");
}
//如果扩展名符合条件，则上传
if (fileOk)
{ FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName); Response.Write("<script>alert('上传成功');</script>");
}

try { //判断是否已经选取文件 if (FileUpload1.HasFile) { if (IsAllowedExtension(FileUpload1)) { string path = Server.MapPath("~/images/"); FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName); Response.Write("<script>alert('上传成功');</script>"); } else { Response.Write("<script>alert('您只能上传jpg或者gif图片');</script>"); } } else { Response.Write("<script>alert('你还没有选择文件');</script>"); } } catch (Exception error) { Response.Write(error.ToString()); } #endregion
}
//真正判断文件类型的关键函数
public static bool IsAllowedExtension(FileUpload hifile)
{ System.IO.FileStream fs = new System.IO.FileStream(hifile.PostedFile.FileName, System.IO.FileMode.Open, System.IO.FileAccess.Read); System.IO.BinaryReader r = new System.IO.BinaryReader(fs); string fileclass = ""; //这里的位长要具体判断. byte buffer; try { buffer = r.ReadByte(); fileclass = buffer.ToString(); buffer = r.ReadByte(); fileclass += buffer.ToString(); } catch { } r.Close(); fs.Close(); if (fileclass == "255216" || fileclass == "7173")//说明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar { return true; } else { return false; } }