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In MVVM (wich makes a lot of things a lot easier - you should try it) you would have two properties in your ViewModel Text that is bound to your TextBox and you would have a ICommand property Apply (or similar) that is bound to the button:

<Button Command="Apply">Apply</Button> 

The ICommand interface has a Method CanExecute that is where you return true if (!string.IsNullOrWhiteSpace(this.Text). The rest is done by WPF for you (enabling/disabling, executing the actual command on click).

The linked article explains it in detail.

In MVVM (wich makes a lot of things a lot easier - you should try it) you would have two properties in your ViewModel Text that is bound to your TextBox and you would have an ICommand property Apply (or similar) that is bound to the button:

<Button Command="Apply">Apply</Button> 

The ICommand interface has a Method CanExecute that is where you return true if (!string.IsNullOrWhiteSpace(this.Text). The rest is done by WPF for you (enabling/disabling, executing the actual command on click).

The linked article explains it in detail.

In MVVM (wich makes a lot of things a lot easier - you should try it) you would have two properties in your ViewModel Text hat is bound to your textbox and you would have a ICommand property Apply or similar that is bound to the button:

<Button Command="Apply">Apply</Button> 

The ICommand interface has a Method CanExecute that is where you return true if (string.IsNullOrWhiteSpace(this.Text). The rest is done by WPF for you.

In MVVM (wich makes a lot of things a lot easier - you should try it) you would have two properties in your ViewModel Text that is bound to your TextBox and you would have a ICommand property Apply (or similar) that is bound to the button:

<Button Command="Apply">Apply</Button> 

The ICommand interface has a Method CanExecute that is where you return true if (!string.IsNullOrWhiteSpace(this.Text). The rest is done by WPF for you (enabling/disabling, executing the actual command on click).

The linked article explains it in detail.

In MVVM (wich makes a lot of things a lot easier - you should try it) you would have two properties in your ViewModel Text hat is bound to your textbox and you would have a ICommand property Apply or similar that is bound to the button:

</Button Command="Apply">Apply</Button> 

The ICommand interface has a Method CanExecute that is where you return true if (string.IsNullOrWhiteSpace(this.Tex). The rest is done by WPF for you.

In MVVM (wich makes a lot of things a lot easier - you should try it) you would have two properties in your ViewModel Text hat is bound to your textbox and you would have a ICommand property Apply or similar that is bound to the button:

<Button Command="Apply">Apply</Button> 

The ICommand interface has a Method CanExecute that is where you return true if (string.IsNullOrWhiteSpace(this.Text). The rest is done by WPF for you.