NullReferanceException with XtraGrid search

[Sl1ver]

By string columnName i get NullReferanceEx ception
What am i doing wrong?

private int GetRowHandleByColumnValue(GridView view, string ColumnFieldName, object value)
        {
             

             string columnName = view.Columns.ColumnByFieldName(ColumnFieldName).Name;
             
                 int result = GridControl.InvalidRowHandle;
                 for (int i = 0; i < view.RowCount; i++)
                     if (view.GetDataRow(i)[columnName].Equals(value))
                         return i;

                 return result;
             
            
        }

        private void btnFind_Click(object sender, EventArgs e)
        {
            string find = "";
            if (cboFind.SelectedItem == "Code")
            {
                find = "AST__Code";
            }
            if (cboFind.SelectedItem == "Barcode")
            {
                find = "AST__Barcode";
            }
            int rowHandle = GetRowHandleByColumnValue(gvAssets, find.ToString(), txtFind.Text);
            if (rowHandle != GridControl.InvalidRowHandle)
            {
                gvAssets.FocusedColumn = gvAssets.Columns.ColumnByFieldName(find.ToString());
                gvAssets.FocusedRowHandle = rowHandle;
                if (gvAssets.IsRowVisible(rowHandle) == RowVisibleState.Hidden)
                    gvAssets.MakeRowVisible(rowHandle, false);
                gvAssets.ShowEditor();
            }
            else
                MessageBox.Show("Item could not be found!");
        }

[r035198x]

Read the NullReferenceEx ception article.