Regular expression for alphanumeric with space in c#

How to validate that string contains only alphanumeric value with some spacial character and with whitespace and how to validate that user can only input alphanumeric with given special character or space in a textbox (like name fields or remarks fields).

In remarks fields we don't want that user can enter anything, user can only able to enter alphanumeric with white space and some spacial character like -,. etc if you allow.

Some of regular expression given below for validating alphanumeric value only, alphanumeric with whitspace only and alphanumeric with whitespace and some special characters.

Alphanumeric regex : ^[a-zA-Z0-9]+$
Alphanumeric with whitspace : ^[a-zA-Z0-9 ]+$
Alphanumeric with given special character : ^[a-zA-Z0-9 ,.'@]+$     (Add spacial character  as you need inside square bracket)

Following code demonstrating the various ways of implementation.

Validate that string contains only alphanumeric value as well as space character through regular expression
public bool IsAlphaNumeric(string inputString)
    Regex r = new Regex("^[a-zA-Z0-9]+$");
    if (r.IsMatch(inputString))
        return true;
        return false;

Verifying that textbox text contains only alphanumeric value as well as space character through Regular Expression Validator in (validation controls).

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

<asp:RegularExpressionValidator ID="REValphaOnly" runat="server" ErrorMessage="Please enter only alphanumeric." ControlToValidate="txtName" ValidationExpression="^[a-zA-Z0-9]+$"></asp:RegularExpressionValidator>

Place regular expression as you need in ValidationExpression fields.

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