i know that the this post almost closed but i think it's not bad to say my solution. this solution is for user that use SQL server as geodatabase. you can manually change it by an SQL update command. all feature's name save in [sde].[GDB_OBJECTCLASSES] table. the alias name set simply if you change the alias column value .

UPDATE [sde].[sde].[GDB_OBJECTCLASSES] 
SET AliasName = 'an alias name' 
WHERE Name='your feature class name'

EDIT: this method is fast method for changing the alias name . but using IClassSchemaEdit is better because in sql update method you can't use alias name until reset feature workspace.

Public Sub SetAliasName(FeatureClass As IFeatureClass, AliasName As String)
        Dim abjTable As ITable = FeatureClass
        Dim objClass As IObjectClass = abjTable
        Dim edit As IClassSchemaEdit = objClass
        edit.AlterAliasName(AliasName)
End Sub

This solution is for user that use SQL server as geodatabase. you can manually change it by an SQL update command. all feature's name save in [sde].[GDB_OBJECTCLASSES] table. the alias name set simply if you change the alias column value .

UPDATE [sde].[sde].[GDB_OBJECTCLASSES] 
SET AliasName = 'an alias name' 
WHERE Name='your feature class name'

EDIT: this method is fast method for changing the alias name . but using IClassSchemaEdit is better because in sql update method you can't use alias name until reset feature workspace.

Public Sub SetAliasName(FeatureClass As IFeatureClass, AliasName As String)
        Dim abjTable As ITable = FeatureClass
        Dim objClass As IObjectClass = abjTable
        Dim edit As IClassSchemaEdit = objClass
        edit.AlterAliasName(AliasName)
End Sub

i know that the this post almost closed but i think it's not bad to say my solution. this solution is for user that use SQL server as geodatabase. you can manually change it by an SQL update command. all feature's name save in [sde].[GDB_OBJECTCLASSES] table. the alias name set simply if you change the alias column value .

UPDATE [sde].[sde].[GDB_OBJECTCLASSES] 
SET AliasName = 'an alias name' 
WHERE Name='your feature class name'

i know that the this post almost closed but i think it's not bad to say my solution. this solution is for user that use SQL server as geodatabase. you can manually change it by an SQL update command. all feature's name save in [sde].[GDB_OBJECTCLASSES] table. the alias name set simply if you change the alias column value .

UPDATE [sde].[sde].[GDB_OBJECTCLASSES] 
SET AliasName = 'an alias name' 
WHERE Name='your feature class name'

EDIT: this method is fast method for changing the alias name . but using IClassSchemaEdit is better because in sql update method you can't use alias name until reset feature workspace.

Public Sub SetAliasName(FeatureClass As IFeatureClass, AliasName As String)
        Dim abjTable As ITable = FeatureClass
        Dim objClass As IObjectClass = abjTable
        Dim edit As IClassSchemaEdit = objClass
        edit.AlterAliasName(AliasName)
End Sub