Webservice method returns error:“There is an error in generating an XML document”

问题

In my application I have used 3-tier architecture using web service. I want o insert a data in the database. When the insert method is called from the webservice it gives an error as "There is an Error in generating an xml document

.CS Save click event

 protected void btnSave_Click(object sender, EventArgs e)
    {
        try
        {
             //assinging values to the Object(objEmp)
            string Result = objEmp.Insert();
            if (Result == "1")
            {

                Page.ClientScript.RegisterStartupScript(this.GetType(), "ShowMessage", string.Format("<script type='text/javascript'>alert('{0}')</script>", "Record Saved"));
                Response.Redirect("ViewEmployeeDetails.aspx");

            }
            else
            {
                Page.ClientScript.RegisterStartupScript(this.GetType(), "Error1", string.Format("<script type='text/javascript'>alert('{0}')</script>", Result.Replace("'", "\\'")));
            }

        }
        catch (Exception ex)
        {
            Page.ClientScript.RegisterStartupScript(this.GetType(), "Error", string.Format("<script type='text/javascript'>alert('{0}')</script>", ex.Message.ToString()));
        }
    }

Class(Emp.cs)

public String Insert()
    {
        Service.SqlParameter[] param = new Service.SqlParameter[13];

        param[0] = new Service.SqlParameter();
        param[0].ParameterName = "@Dta_Users";
        param[0].Value = Dta_Users;
        param[0].SqlDbType = Service.SqlDbType.NVarChar;

        param[1] = new Service.SqlParameter();
        param[1].ParameterName = "@FK_EmployeeTypeID";
        param[1].Value = FK_EmployeeTypeID;
        param[1].SqlDbType = Service.SqlDbType.Decimal;

        param[2] = new Service.SqlParameter();
        param[2].ParameterName = "@EmployeeName";
        param[2].Value = EmployeeName;
        param[2].SqlDbType = Service.SqlDbType.NVarChar;

        param[3] = new Service.SqlParameter();
        param[3].ParameterName = "@CellNo";
        param[3].Value = CellNo;
        param[3].SqlDbType = Service.SqlDbType.NVarChar;

        param[4] = new Service.SqlParameter();
        param[4].ParameterName = "@PhNo";
        param[4].Value = PhNo;
        param[4].SqlDbType = Service.SqlDbType.NVarChar;

        param[5] = new Service.SqlParameter();
        param[5].ParameterName = "@Address";
        param[5].Value = Address;
        param[5].SqlDbType = Service.SqlDbType.NVarChar;

        param[6] = new Service.SqlParameter();
        param[6].ParameterName = "@Email";
        param[6].Value = Email;
        param[6].SqlDbType = Service.SqlDbType.NVarChar;

        param[7] = new Service.SqlParameter();
        param[7].ParameterName = "@DOB";
        if (DOB == null)
        {
            param[7].Value = DBNull.Value;
        }
        else
        {
            param[7].Value = DOB;
        }
        param[7].SqlDbType = Service.SqlDbType.DateTime;

        param[8] = new Service.SqlParameter();
        param[8].ParameterName = "@DOJ";
        param[8].Value = DOJ;
        param[8].SqlDbType = Service.SqlDbType.DateTime;

        param[9] = new Service.SqlParameter();
        param[9].ParameterName = "@DOR";
        param[9].Value = DOR;
        param[9].SqlDbType = Service.SqlDbType.NVarChar;

        param[10] = new Service.SqlParameter();
        param[10].ParameterName = "@Status";
        param[10].Value = Status;
        param[10].SqlDbType = Service.SqlDbType.NVarChar;

        param[11] = new Service.SqlParameter();
        param[11].ParameterName = "@Remarks";
        param[11].Value = Remarks;
        param[11].SqlDbType = Service.SqlDbType.NVarChar;

        param[12] = new Service.SqlParameter();
        param[12].ParameterName = "@Dta_User";
        param[12].Value = Dta_User;
        param[12].SqlDbType = Service.SqlDbType.NVarChar;

        return  s.InsUpdDel(Conn, "Employee_Insert", param);


    }

webservice method [WebMethod]

public string InsUpdDel(string Conn, string ProcName, SqlParameter[] p)
{
    try
    {
        using (SqlConnection cn = new SqlConnection(Conn))
        {
            if (cn.State == ConnectionState.Open || cn.State == ConnectionState.Broken || cn.State == ConnectionState.Connecting || cn.State == ConnectionState.Executing || cn.State == ConnectionState.Fetching)
                cn.Close();
            cn.Open();
            SqlCommand cmd = new SqlCommand(ProcName, cn);

            cmd.CommandType = CommandType.StoredProcedure;

            foreach (SqlParameter param in p)
            {
                cmd.Parameters.Add(param);
            }
            SqlDataReader dr = cmd.ExecuteReader();
            dr.Read();
            if (dr[0].ToString() == "1")
            {
                return "1";
            }
            else
            {
                return dr[0].ToString();
            }
            //dr.Close();
            cn.Close();
        }
    }
    catch (Exception ex)
    {
        return "Error : " + ex.Message.ToString();
    }


}

When i debug the save_click event the cursor goes to the catch statement....as the error is from web service. If i simply add InsUpdDel() method in Emp.cs and call this method in Insert() method then error is not coming

If i write below code then its giving error

        param[7] = new Service.SqlParameter();
        param[7].ParameterName = "@DOB";
        if (DOB == null)
        {
            param[7].Value = DBNull.Value;
        }
        else
        {
            param[7].Value = DOB;
        }
        param[7].SqlDbType = Service.SqlDbType.DateTime;

if i write below code then its not giving error

    param[7] = new Service.SqlParameter();
    param[7].ParameterName = "@DOB";
    param[7].Value = DOB;
    param[7].SqlDbType = Service.SqlDbType.DateTime;

回答1:

Change this line:

param[7].Value = DBNull.Value;

to

param[7].Value = null;

And then on ws side:

foreach (SqlParameter param in p)
{
    if (param.Value == null)
    {
           param.Value = DBNull.Value;
    }
    cmd.Parameters.Add(param);
}

来源：https://stackoverflow.com/questions/15020551/webservice-method-returns-errorthere-is-an-error-in-generating-an-xml-document