c# - LINQ to SQL Failing to Insert to the Database -

i learning linq , trying insert using linq sql having challenges when inserting showing me incorrect string format when debug no pointing on specific line. can please me made mistake.

save button

            list<legal_member> _legalmemberlist = _dc.legal_members.where(a => a.idnumber == txtidnumber.text.tostring()).tolist();              if (rbtnareyouemployed.items[0].selected == true)             {                 viewstate["areyouemployed"] = true;             }             else             {                 viewstate["areyouemployed"] = false;             }              if (rbtnissacitizen.items[0].selected == true)             {                 viewstate["issacitizen"] = true;             }             else             {                 viewstate["issacitizen"] = false;             }             if (_legalmemberlist != null)             {                 if (_legalmemberlist.count() == 0)                 {                     legal_member _legalmember = new legal_member                     {                         idnumber = txtidnumber.text,                         inceptiondate = convert.todatetime(txtinceptiondate.text),                         legalpreferedname = txtpreferedname.text,                         initials = txtinitials.text,                         titleid = int.parse(cbotitle.selectedvalue),                         fullnames = txtfullnames.text,                         surname = txtsurname.text,                         age = int.parse(txtage.text),                         dateofbirth = convert.todatetime(txtdateofbirth.text),                         passportnumber = txtpassport.text,                         areyouemployed = bool.parse(viewstate["areyouemployed"].tostring()),                         employer = txtemployer.text,                         contactnumber = txtcontactnumber.text,                         othercontanctnumber = txtothercontanctnumber.text,                         emailaddress = txtemailaddress.text,                         issacitizen = bool.parse(viewstate["issacitizen"].tostring()),                         telephonework = txttelephonework.text,                         telephonehome = txttelephonehome.text,                     };                      _dc.legal_members.insertonsubmit(_legalmember);                     _dc.submitchanges(); 

sql table

create table [dbo].[legal_member]( [legalmembershipid] [int] identity(1,1) not null, [inceptiondate] [datetime] null, [legalpreferedname] [nvarchar](50) null, [initials] [nvarchar](50) null, [titleid] [int] null, [fullnames] [nvarchar](50) null, [surname] [nvarchar](50) null, [age] [int] null, [dateofbirth] [datetime] null, [idnumber] [nvarchar](50) null, [passportnumber] [nvarchar](50) null, [areyouemployed] [bit] null, [employer] [nvarchar](50) null, [contactnumber] [nvarchar](50) null, [othercontanctnumber] [nvarchar](50) null, [emailaddress] [nvarchar](50) null, [issacitizen] [bit] null, [telephonework] [nvarchar](50) null, [telephonehome] [nvarchar](50) null) 

i don't think need line: try insert after removing line:

       legalmembershipid = int.parse(txtmembershipnumber.text)  

as primary key field auto increment. please remove , try insert.