mysql - C# Syntax issue in my If statment -

im having issues if statment , 1 in think main issue in:

(string.isnullorwhitespace(txtfirstname.text) || string.isnullorwhitespace(txtlastname.text) || string.isnullorwhitespace(txtemail.text) || string.isnullorwhitespace(txthotel.text))

i want if statements false should execute mysql command (ps working moment syntax fells wrong.)

        if (appointment.checkstate == checkstate.checked)         {             if (string.isnullorwhitespace(txtfirstname.text))             {                 txtfirstname.backcolor = color.red;                 messagebox.show("please enter first name!");             }             else             {                 txtfirstname.backcolor = color.white;             }             if (string.isnullorwhitespace(txtlastname.text))             {                 txtlastname.backcolor = color.red;                 messagebox.show("please enter last name!");             }             else             {                 txtlastname.backcolor = color.white;             }              if (string.isnullorwhitespace(txtemail.text))             {                 txtemail.backcolor = color.red;                 messagebox.show("please enter email!");             }             else             {                 txtemail.backcolor = color.white;             }              if (string.isnullorwhitespace(txthotel.text))             {                 txthotel.backcolor = color.red;                 messagebox.show("please enter valid hotel!");             }             else             {                 txthotel.backcolor = color.white;                 }                if (string.isnullorwhitespace(txtfirstname.text) || string.isnullorwhitespace(txtlastname.text) || string.isnullorwhitespace(txtemail.text) || string.isnullorwhitespace(txthotel.text))              {              }             else             {                 ///register client                 connect.open();                 mysqlcommand command = new mysqlcommand("insert client (firstname,lastname,nationality,mobile,email,budget,comments) value(@firstname,@lastname,@nationality,@mobile,@email,@budget,@comments)", connect);                 command.parameters.addwithvalue("@firstname", txtfirstname.text);                 command.parameters.addwithvalue("@lastname", txtlastname.text);                 command.parameters.addwithvalue("@nationality", txtnationality.text);                 command.parameters.addwithvalue("@mobile", txtmobile.text);                 command.parameters.addwithvalue("@email", txtemail.text);                 command.parameters.addwithvalue("@budget", int.parse(txtbudget.text));                 command.parameters.addwithvalue("@comments", txtcomments.text);                   command.executenonquery();                 connect.close();                  loadclient();                    ///register appointment                 connect.open();                 command = new mysqlcommand("insert appointment(hotel,roomnumber,appointmentdate,appointmenttime,confirmby,propertytype,bedrooms,purpose,interestedin,departuredate) value(@hotel,@roomnumber,@appointmentdate,@appointmenttime,@confirmby,@propertytype,@bedrooms,@purpose,@interestedin,@departuredate)", connect);                 command.parameters.addwithvalue("@hotel", txthotel.text);                 command.parameters.addwithvalue("@roomnumber", int.parse(txtroomnumber.text));                 command.parameters.addwithvalue("@appointmentdate", datetimepicker2.value.date);                 command.parameters.addwithvalue("@appointmenttime", cmbtimeapp.text);                 command.parameters.addwithvalue("@confirmby", cmbconfirm.text);                 command.parameters.addwithvalue("@propertytype", cmbpropertytype.text);                 command.parameters.addwithvalue("@bedrooms", cmbbedroom.text);                 command.parameters.addwithvalue("@purpose", cmbpurpose.text);                 command.parameters.addwithvalue("@interestedin", cmbintrestedin.text);                 command.parameters.addwithvalue("@departuredate", datetimepicker3.value.date);                  command.executenonquery();                 connect.close();                  messagebox.show("appointment registered!");             }            } 

obviously logic expression of type:

if  (condition1 || condition2 || condition3 || ....)  {     doa();    } else {     dob(); } 

can transformed to:

if  (!condition1 && !condition2 && !condition3 && ....)  {     dob();    } else {     doa(); } 

this solve problem code readability still suspect

if (!string.isnullorwhitespace(txtfirstname.text) &&     !string.isnullorwhitespace(txtlastname.text) &&     !string.isnullorwhitespace(txtemail.text) &&      !string.isnullorwhitespace(txthotel.text)) {     //... }  

yuck!

how can improve this? using auxiliary local variables makes code easier read; highlights semantics of code , hides mechanics. locals extremely cheap (or free), use them!

consider following approach:

var isvalidfirstname = !string.isnullorwhitespace(txtfirstname.text) var isvalidlastname = !string.isnullorwhitespace(txtlastname.text) var isvalidemail = !string.isnullorwhitespace(txtemail.text) var isvalidhotel = !string.isnullorwhitespace(txthotel.text)) 

and if statement looks this:

if (isvalidfirstname &&     isvalidlastname &&     isvalidemail &&      isvalidhotel) {     //... } 

doesn't read better?

but why stop here? can't abstract whole guest info validation away? sure can:

public static bool isvalidguestinfo(string firstname, string lastname, string email, string hotel) {      var isvalidfirstname = !string.isnullorwhitespace(txtfirstname.text)      var isvalidlastname = !string.isnullorwhitespace(txtlastname.text)      var isvalidemail = !string.isnullorwhitespace(txtemail.text)      var isvalidhotel = !string.isnullorwhitespace(txthotel.text))       return isvalidfirstname && isvalidlastname && isvalidemail && isvalidhotel; } 

and if statement simply:

 if (isvalidguestinfo(firstname, lastname, email, hotel))  {      //...  } 

now reads better, semantics clear , mechanisms used not in way. also, boot, if need validate guest info anywhere else in code not need duplicate code.