How to add a RequiredFieldValidator to DropDownList control

Question

I have a DropDownList binded with aSqlDataSource to display the values from the database   I am unable to validate using a RequiredFieldValidator

User · Answer

InitialValue  0    initial validation will fire when 0th index item is selected in ddl    lt asp RequiredFieldValidator InitialValue  0  Display  Dynamic  CssClass  error  runat  server  ID  your id  ValidationGroup  validationgroup  ControlToValidate  your dropdownlist id    gt

User · Answer

For the most part you treat it as if you are validating any other kind of control but use the InitialValue property of the required field validator    lt asp RequiredFieldValidator ID  rfv1  runat  server  ControlToValidate  your-dropdownlist  InitialValue  Please select  ErrorMessage  Please select something    gt    Basically what it s saying is that validation will succeed if any other value than the 1 set in InitialValue is selected in the dropdownlist   If databinding you will need to insert the  Please select  value afterwards as follows  this ddl1 Items Insert 0   Please select

User · Answer

Suppose your drop down list is    lt asp DropDownList runat  server  id  ddl  gt   lt asp ListItem Value  0  text  Select a Value  gt        lt  asp DropDownList gt    There are two ways    lt asp RequiredFieldValidator ID  re1  runat  Server  InitialValue  0    gt    the 2nd way is to use a compare validator    lt asp CompareValidator ID  re1  runat  Server  ValueToCompare  0  ControlToCompare  ddl  Operator  Equal    gt

User · Answer

If you are using a data source  here s another way to do it without code behind   Note the following key points    The ListItem of Value  0  is on the source page  not added in code The ListItem in the source will be overwritten if you don t include AppendDataBoundItems  true  in the DropDownList InitialValue  0  tells the validator that this is the value that should fire that validator  as pointed out in other answers    Example    lt asp DropDownList ID  ddlType  runat  server  DataSourceID  sdsType                    DataValueField  ID  DataTextField  Name  AppendDataBoundItems  true  gt       lt asp ListItem Value  0  Text  --Please Select--  Selected  True  gt  lt  asp ListItem gt   lt  asp DropDownList gt   lt asp RequiredFieldValidator ID  rfvType  runat  server  ControlToValidate  ddlType                               InitialValue  0  ErrorMessage  Type required  gt  lt  asp RequiredFieldValidator gt   lt asp SqlDataSource ID  sdsType  runat  server                      ConnectionString   lt    ConnectionStrings TESTConnectionString   gt                      SelectCommand  SELECT ID  Name FROM Type  gt  lt  asp SqlDataSource gt

[asp.net] How to add a RequiredFieldValidator to DropDownList control?

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