The error clearly saying, There is no overload for method insert with 4 arguments.
Did you give method definition of insert with 4 arguments which is of string type?
public void insert(string _name, string _add,string _city,string _email)
//your code to insert
My suggestion is debug your code, where exactly it is giving error, so you will come to know if there is no method? or If method is there any issue with parameters or return type, etc
Hope this will help you
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