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How to limit maximum and minimum number of text in asp.net textbox?

I am trying to limit the number of text into a Textbox field. The requirement is to fix the minimum length as 7 and maximum length as 15.
I have tried to use the asp:RegularExpressionValidator to limit the number of text into the textbox.
Here is my code:
<asp:RegularExpressionValidator ID="revphone" runat="server"
Font-Size="16px"
ValidationExpression="^[0-9]{7,15}$"
ControlToValidate="txtphonenumber"
ErrorMessage="*"
ValidationGroup="reg"
Display="Dynamic"
ForeColor="Red">
</asp:RegularExpressionValidator>Phone Number
<asp:TextBox ID="txtphonenumber" runat="server"
placeholder="Phone Number"
Width="305px"
onblur="BtnRegisterClick()"
MaxLength="7">
</asp:TextBox>
I am able to get the minimum number but not getting the maximum number. It is limiting to type 7 digits only.

Here is Your Solution:-
<asp:TextBox ID="txtphonenumber" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator Display = "Dynamic" ControlToValidate = "txtphonenumber" ID="revphone" ValidationExpression = "^[\s\S]{7,15}$" runat="server" ErrorMessage="Minimum 7 and Maximum 15 characters required."></asp:RegularExpressionValidator>
For More Info Refer this Below Link.....
https://www.aspsnippets.com/Articles/TextBox-Minimum-and-Maximum-Character-Length-Validation-using-ASPNet-RegularExpression-Validators.aspx

How to write a RegularExpressionValidator for a 10 Digits mobile number?

I am a new ASP.NET Webforms developer and I am struggling right now with validating the TextBox control that asks for a mobile phone number. There is only one format used when entering a phone number which is
05# ### ####
I would like to use ASP.NET RegularExpressionValidator control with this TextBox and I need to a regular expression that matches the preceding expressions. The regular expression should validate the entered number against the following rules:
The preceding format
The number must start with 05
The number must be of 10 digits only
So how can I write a regular expression (or ValidationExpression) property for this ASP.NET RegularExpressionValidator control?
Here's a snippet of my work:
<asp:TextBox ID="txtPhoneNew" runat="server" CssClass="form-control" placeholder="966 ## ### ####"></asp:TextBox>
<asp:RegularExpressionValidator ID="revPhoneNew" runat="server"
ControlToValidate="txtPhoneNew" ErrorMessage="Enter a valid mobile phone number"
ValidationExpression="[0-9]{10}"></asp:RegularExpressionValidator>

as Tim stated, and per your example the regular expression you need is
<asp:TextBox ID="txtPhoneNew" runat="server" CssClass="form-control" placeholder="966 ## ### ####"></asp:TextBox>
<asp:RegularExpressionValidator ID="revPhoneNew" runat="server"
ControlToValidate="txtPhoneNew" ErrorMessage="Enter a valid mobile phone number"
ValidationExpression="^05\d{3}\s\d{4}$"></asp:RegularExpressionValidator>

try this
<asp:TextBox ID="txtPhoneNew" MaxLength="10" runat="server" CssClass="form-control" ></asp:TextBox>
<asp:RegularExpressionValidator ID="RegularExpressionValidator1"
runat="server" ControlToValidate="txtPhoneNew"
ErrorMessage="enter valid phone" ValidationExpression="^05[0-9]{8}$"></asp:RegularExpressionValidator>

ASP.NET date validator passing when it should not

I'm using a RegularExpressionValidator in ASP.NET. I have these validators for my asp:Textbox control:
<asp:RangeValidator
ID="rvDate"
runat="server"
ControlToValidate="txtCrimeDate"
Type="Date"
ErrorMessage="Must be within latest three months"
Display="Dynamic"
OnInit="RangeValidator_Init">
</asp:RangeValidator>
<asp:RegularExpressionValidator
ID="revDate"
runat="server"
ControlToValidate="txtCrimeDate"
Display="Dynamic"
ErrorMessage="Must be in format YYYY-MM-DD"
ValidationExpression="[0-9]{4}-[0-9]{2}-[0-9]{2}">
</asp:RegularExpressionValidator>
I have set the min and max value of the RangeValidator in the code-behind and it works as intended. But! If I enter something with 2 numbers for the year, like 15-11-28 everything passes, even the other validators for the other controls. Any ideas?

Check the date format (US or otherwise) and 0-9 for the day and month are incorrect eg:
2013-99-99
Look into using the CompareValidator control, this is mainly used for string matching, but can be made to check between two date ranges.

How can i prevent only html tags which does not include numbers, so how can i allow numbers

I set validation expression ValidationExpression="<(.|\n)*?>" but it does not give permission to numbers how can i solve it?
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="TextBox1" ErrorMessage="RegularExpressionValidator" ValidationExpression="^[a-zA-Z''-'\s]{1,40}$"></asp:RegularExpressionValidator><br />

Instead of (.|\n)*, use \D*.

Why isn't my RangeValidator working?

I succesfully used a validator more than once,but after some programming my validators are not working.Maybe is something i don't know about defining 2 validators for the same control, but it doesn't work for one validator in a control either.Here are 2 examples of my code:
Example 1: one required field validator and one "maximum value" validator for username:
<asp:RequiredFieldValidator id="UsernameRequiredValidator" runat="server"
ControlToValidate="UserNameTextbox" ForeColor="red"
Display="Dynamic" ErrorMessage="Required" />
<asp:RangeValidator ID="RangeValidator1" runat="server" ControlToValidate="UsernameTextbox" MinimumValue="1" MaximumValue="20" ForeColor="red"
Display="Dynamic" ErrorMessage="Name must contain maximum 20 characters"></asp:RangeValidator>
Example 2: one "maximum value" validator for roadaddress(string):
<asp:RangeValidator ID="RangeValidator9" runat="server" MaximumValue="50" ForeColor="red"
ErrorMessage="Road Address must contain maxmum 50 characters" ControlToValidate="RoadAddressTextbox"></asp:RangeValidator>
I am thinking that the problem is maybe in the display property or in the causesvalidation property which i don't use...

That's not what the RangeValidator is used for. The RangeValidator is intended to check input to make sure it's within a certain range, i.e. to make sure that a number is between 1 and 5, that a date is within a certain range, etc.
What you need is a RegularExpressionValidator:
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server"
ControlToValidate="UserNameTextbox"
ErrorMessage="Username must be between 1 and 50 characters"
ValidationExpression="^[a-zA-Z\s]{1,50}">
</asp:RegularExpressionValidator>
EDIT: Updated expression to ^[a-zA-Z\s]{1,50}

RangeValidators don't validate the number of characters in the input, they "Check whether the value of an input control is within a specified range of values."
You can actually do this without a Validator, by setting the MaxLength property on the text box which would limit the number of characters entered into it.
<asp:TextBox ID="UserNameTextbox" MaxLength="50" runat="server"></asp:TextBox>