How to work with null incoming from database

Question

I'm getting this error

This method or property cannot be called on Null values

on this line id = rd.GetString(0);. How to solve it?

public string MaxId()
{
    string id = "";

    con.Open();
    string sql = "SELECT MAX(id) FROM Customer";
    SqlCommand cmd = new SqlCommand(sql, con);
    SqlDataReader rd = cmd.ExecuteReader();
    while (rd.Read()){
        id = rd.GetString(0);
    }
    con.Close();
    return id;
}

This might help - http://stackoverflow.com/questions/1772025/sql-data-reader-handling-null-column-values — kelsier, Dec 14 '13 at 06:44

Ehsan · Answer 1 · 2013-12-14T06:52:20.210

add this

!rd.IsDBNull(0)

before

id = rd.GetString(0);

So, your code would look like

public string MaxId()

    {
    string id = "";

    con.Open();
    string sql = "SELECT MAX(id) FROM Customer";
    SqlCommand cmd = new SqlCommand(sql, con);
    SqlDataReader rd = cmd.ExecuteReader();
    while (rd.Read())

    {
        if(!rd.IsDBNull(0))
            id = rd.GetString(0);
    }
    con.Close();
    return id;

How to work with null incoming from database

1 Answers1