Convert date time into date:Post method showing failed

I am new to react and web api development. I am having an issue with datetime. As I am having a datetime component in my employee model.

Code here:

Employee.cs

namespace WebAPI.Models
{
    public class Employee
    {
        public long EmployeeID { get; set; }
        public string EmployeeName { get; set; }

        public string Department { get; set; }
        public string MailID { get; set; }
        public DateTime DOJ { get; set; }

    }
}
 

I am trying to add the elements from a modal popup to my database using the employee controller. However, I think it is failing due to the popup accepting date and the web api passing date time .Hence there is a mismatch when inserting. I tried to resolve this issue by adding this code below to employee controller.

string doj = emp.DOJ.ToString().Split(' ')[0];

Here is my employee controller part:

public string Post(Employee emp)
        {
            try
            {
                DataTable table = new DataTable();

                string doj = emp.DOJ.ToString().Split(' ')[0];

                string query = @"
                insert into dbo.Employees
                (EmployeeName,
                Department,
                MailID,
                DOJ)
                Values
                (
                 '" + emp.EmployeeName + @"',
                 '" + emp.Department + @"',
                 '" + emp.MailID + @"',
                 '" + doj + @"'
                 )
                    ";

                using (var con = new SqlConnection(ConfigurationManager.ConnectionStrings["EmployeeAppDB"].ConnectionString))
                using (var cmd = new SqlCommand(query, con))
                using (var da = new SqlDataAdapter(cmd))
                {
                    cmd.CommandType = CommandType.Text;
                    da.Fill(table);


                }
                return "Added Successfully";
            }
            catch (Exception )
            {
                return "Failed to Add";
            }
        }

Here is what I am using in visual studio code:

class AddEmpModal extends Component{
    constructor(props){
        super(props);
    
        this.state = {deps:[],sanackbaropen: false, snackbarmsg:''};
    
        this.handleSubmit = this.handleSubmit.bind(this);
        }

         componentDidMount()
         {
             fetch('https://localhost:44363/api/department')
             .then(response=> response.json())
             .then(data=>{
              this.setState({deps:data});

             });
         }

        snackbarClose = (event) =>{
            this.setState({snackbaropen:false});
          };

        

        handleSubmit(event){
            event.preventDefault();
    
            fetch('https://localhost:44363/api/Employee',{
            
            method:'POST',
            headers:{
                'Accept':'application/json',
                'Content-Type':'application/json'
    
            },
            body:JSON.stringify({
              EmployeeID:null,
              EmployeeName: event.target.EmployeeName.value,
              Department: event.target.Department.value,
              MailID: event.target.MailID.value,
              DOJ: event.target.DOJ.value,
            })
          })
            .then(res=> res.json())
            .then((result)=>
            {
              //alert(result);
              this.setState({snackbaropen:true,snackbarmsg:result})
            },
            (error)=>{
             // alert('Failed')
             this.setState({snackbaropen:true,snackbarmsg:'failed'})
          
            })
        }

Could you tell me a way to solve the datetime issue or tell me where I am going wrong?