首先，我会更改您的查询以使用参数化命令

First of all, I would change your query to use a parameterized command

    da = New Odbc.OdbcDataAdapter("Select distinct lname FROM tblemployee WHERE emp_id =?", con)
    da.SelectCommand.Parameters.AddWithValue("@p1", TextBox1.Text.Trim())
    dr = cmd.ExecuteReader
    If dr.Read Then

        txtlname.Text = dr("lname").ToString
        txtlname.Refresh()
    Else
        MessageBox.Show("No record found!")
    End If

然后，我添加了一条消息，以防 dr.Read 返回 false.(没有符合 where 条件的记录)至少你会知道文本框保持空白是否有一个简单的原因.

Then, I have added a message in case dr.Read return false. (No record matching the where condition) At least you will know if there is a simple reason why the textbox remains blank.

最后一点.如果 emp_id 是表 tblEmployee 中的数字字段，则传递给 SelectCommand 参数集合的值应转换为整数，因为原样，它作为字符串传递，这可能是丢失结果的来源.

A final note. If emp_id is a numeric field in the table tblEmployee the value passed to the SelectCommand parameters collection should be converted to an intenger because, as is, it is passed as a string and this could be the source of missing results.