为什么我在添加信息时，会出现这样个错误：
发生类型为System.Web.HttpUnhandledException的异常

private void add_Click(object sender, System.EventArgs e)
{ strsql="insert into users(username,sex,hometown,nation,birth,health,marry,political,address,mobilephone,homephone,email,gra_school,zhuanye,xueli,gra_time,work_time,dep_name,zhiwu,type,constract_time,cancel_time,PicUrl) values ( ";

strsql+="'" + username.Text + "'";
strsql+="'" + sex.SelectedValue + "'";
strsql+="'" + hometown.Text + "'";
strsql+="'" + nation.Text + "'";
strsql+="'" + birth.Text + "'";
strsql+="'" + health.Text + "'";
strsql+="'" + marry.SelectedValue + "'";
strsql+="'" + political.Text + "'";
strsql+="'" + address.Text + "'";
strsql+="'" + mobilephone.Text + "'";
strsql+="'" + homephone.Text + "'";
strsql+="'" + email.Text + "'";
strsql+="'" + gra_school.Text + "'";
strsql+="'" + zhuanye.Text + "'";
strsql+="'" + xueli.SelectedValue + "'";
strsql+="'" + gra_time.Text + "'";
strsql+="'" + work_time.Text + "'";
strsql+="'" + dep_name.SelectedValue + "'";
strsql+="'" + zhiwu.Text + "'";
strsql+="'" + type.SelectedValue + "'";
strsql+="'" + constract_time.Text + "'";
strsql+="'" + cancel_time.Text + "'";
strsql+=url;
strsql+=")";

com=new SqlCommand(strsql,conn);
conn.Open();
com.ExecuteNonQuery();
com.Dispose();
conn.Close();
Response.Write("<script>javascript:alert('添加成功！！！');</script>");
// Response.Redirect("add_person.aspx?users_id=");
}

private void add_Click(object sender, System.EventArgs e)
{
try
{
string strsql;

strsql="insert into users(username,sex,hometown,nation,birth,health,marry,political,address,mobilephone,homephone,email,gra_school,zhuanye,xueli,gra_time,work_time,dep_name,zhiwu,type,constract_time,cancel_time,PicUrl)";
strsql+=" + values( +";

strsql+="'" + username.Text + "'";
strsql+="'" + sex.SelectedValue + "'";
strsql+="'" + hometown.Text + "'";
strsql+="'" + nation.Text + "'";
strsql+="'" + birth.Text + "'";
strsql+="'" + health.Text + "'";
strsql+="'" + marry.SelectedValue + "'";
strsql+="'" + political.Text + "'";
strsql+="'" + address.Text + "'";
strsql+="'" + mobilephone.Text + "'";
strsql+="'" + homephone.Text + "'";
strsql+="'" + email.Text + "'";
strsql+="'" + gra_school.Text + "'";
strsql+="'" + zhuanye.Text + "'";
strsql+="'" + xueli.SelectedValue + "'";
strsql+="'" + gra_time.Text + "'";
strsql+="'" + work_time.Text + "'";
strsql+="'" + dep_name.SelectedValue + "'";
strsql+="'" + zhiwu.Text + "'";
strsql+="'" + type.SelectedValue + "'";
strsql+="'" + constract_time.Text + "'";
strsql+="'" + cancel_time.Text + "'";
strsql+="'" + url + "'";
strsql+=")";
com=new SqlCommand(strsql,conn);
conn.Open();
com.ExecuteNonQuery();

Response.Write("<script>javascript:alert('添加成功！！！');</script>");
Response.Redirect("default.aspx");
}
catch(Exception ee)
{
Response.Write("出现异常错误!");
throw ee;
}

}
com.Dispose();
conn.Close();
}

我加入信息后，就是那个错
sql语句是不是应该改成：

strsql="insert into users(username,sex,hometown,nation,birth,health,marry,political,address,mobilephone,homephone,email,gra_school,zhuanye,xueli,gra_time,work_time,dep_name,zhiwu,type,constract_time,cancel_time,PicUrl)";
strsql+=" + values( +";

strsql+="'" + username.Text + "'";
strsql+=","; //是不是都加入这句
strsql+="'" + sex.SelectedValue + "'";
strsql+="'" + hometown.Text + "'";
strsql+="'" + nation.Text + "'";
strsql+="'" + birth.Text + "'";
strsql+="'" + health.Text + "'";
strsql+="'" + marry.SelectedValue + "'";
strsql+="'" + political.Text + "'";
strsql+="'" + address.Text + "'";

strsql+= username.Text + "',' ";
strsql+= sex.SelectedValue + "') ";
还是用这个清楚点，比
strsql+="'" + username.Text + "',' ";
strsql+= sex.SelectedValue + "',' ";
........
清楚