There are many ways to validate and force users to type only Numeric data.  You have Bootstrap, MVC, Text Boxes with the attribute of, TextMode="Number", 3rd party controls with Mask Edit such as DevExpress, Infragistics, and others.

The problem with some of these options is that they only work on browsers that support HTML5, some don't play well with IE. In the case of the mask editors I have found these to be very clunky such as you have to hit back space to enter data, delete does not work, or it seems the entry just locks up. 

I own DevExpress but prefer to use the JavaScript method discussed below. It handles the data entry much nicer. 

There is an old standby that I have used from mredkj. It is basically a very well written JavaScript that allows numeric entry only, optional decimal positions allowed as well as prevent negative numbers if you chose to do so.

You can test it out that mredkj blog at this link.

EXAMPLE:

1. Add JS File to your project

 <script src="Scripts/ValidateNumber.js" type="text/javascript" ></script> 

2. Add a TextBox to a page.

<asp:TextBox ID="TxtValScript" runat="server"></asp:TextBox>

3. In the code behind attach to the JavaScript (you can include or exclude decimals / negative values)

TxtValScript.Attributes.Add("onblur", "extractNumber(this,2,false);");
TxtValScript.Attributes.Add("onkeyup", "extractNumber(this,2,false);");
TxtValScript.Attributes.Add("onkeypress", "return blockNonNumbers(this,event,true,false);");
TxtValScript.MaxLength = 8;

The attached ZIP file has the JavaScript. 

Validation.zip (1.64 kb)