ArcEngine属性表显示问题

[ycyiyue]

public partial class attribute : Form
{

private ILayer layer;

public attribute(ILayer lyr)
{
InitializeComponent();
layer = lyr;

// this.Text = "\"" + layer.Name + "\" 属性表";

}

private void attribute_Load(object sender, EventArgs e)
{
// try
{

ITable lyrtable = (ITable)layer;
DataTable table = new DataTable();
IField field;
for (int i = 0; i < lyrtable.Fields.FieldCount; i++)
{
field = lyrtable.Fields.get_Field(i);
table.Columns.Add(field.Name);
}
object[] values = new object[lyrtable.Fields.FieldCount];
IQueryFilter queryFilter = new QueryFilter();
ICursor cursor = lyrtable.Search(queryFilter, true);
IRow row;
while ((row = cursor.NextRow()) != null)
{
for (int j = 0; j < lyrtable.Fields.FieldCount; j++)
{
object ob = row.get_Value(j);
values[j] = ob;
}
table.Rows.Add(values);
}
this.dataGridView1.DataSource = table;
}
// catch
//{
// MessageBox.Show("无法显示属性表！");
// this.Close();
}
}
无法打开属性变
问题在这行代码
for (int i = 0; i < lyrtable.Fields.FieldCount; i++)；
提示未将对象引用设置到对象的实例。
求解答