Somehow I get a feeling you are talking about binding...
You can bind to Textboxes just like you can bind to DataGridViews.
TextBox1.Bindings.Add("Text", MyDataSourceObject, "MyDataSourceProperty")
Alternatively you can add Bindings from the Property Grid. Look for (DataBindings).
It is called Simple Binding.
Data binding concepts in .NET windows forms[
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Alternatively, without binding, you could simply fetch a DataRow from your database and pretty much assign a columns value to your TextBox.Text Property.